Modern day marine VHF radios not only offer basic transmit and receive capabilities, many package additional features that truly make these radios indispensable for the mariner. For the last several years all fixed mount marine VHF radios have required by certification some level of "" (DSC) calling capability. Even the basic set has the ability to alert other boats, ships, and shore stations with a single button press. More expensive radios offer far more extensive DSC capabilities. These may include position polling or a variety of group calling options. Most mid-priced marine VHF radios integrate other features too. Many have the ability to connect to a remote microphone and act as an intership intercom system. Still others have a built-in hailer that when connected to an external hailer horn can act as a public address system and/or output required fog signals when conditions warrant. The most sophisticated marine VHF radios have an alphanumeric keypad for data entry, are able to connect to optional voice scramblers, and a few even have the ability to use a Bluetooth headset. The newest combination of features offered is the integration of a complete unit with a marine VHF radio.
Marine VHF radio is installed on all large ships and most seagoing small craft. It is used for a wide variety of purposes, including summoning services and communicating with harbours, , and , and operates in the frequency range, between 156 to 174 MHz. Although it is widely used for collision avoidance, its use for this purpose is contentious and is strongly discouraged by some countries, including the UK.
Tune your radio to Channel 16. Distress signal "MAYDAY", (spoken three times). The words "THIS IS", spoken once. Name of vessel in distress (spoken three times). Give position of vessel by latitude or longitude or by bearing (true or magnetic, state which) and distance to a well-known landmark such as a navigational aid or small island, or in any terms which will assist a responding station in locating the vessel in distress. Include any information on vessel movement such as course, speed and destination. Provide nature of distress (sinking, fire etc.). Indicate number of persons onboard. Provide kind of assistance desired. Any other information which might facilitate rescue, such as length or tonnage of vessel, number of persons needing medical attention, color hull, cabin, masts, etc. The word "OVER".Stay by the radio if possible. Even after the message has been received, the USCG can find you more quickly if you can transmit a signal on which a rescue boat or aircraft can home in on.An Example of a Mayday CallDo Not Use Cellular Phones!
Cellular phones are not a sufficient substitute for a VHF Marine Radio.