Marine VHF radio

It is used for a wide variety of purposes, including marine navigation and traffic control, summoning rescue services and communicating with harbours, locks, bridges and marinas.

Marconi built a string of shore stations and in 1904 established the first Morse code distress call, the letters CQD, used until 1906 when SOS was agreed on.

The first significant marine rescue due to radio was the 1909 sinking of the luxury liner RMS Republic, in which 1,500 lives were saved.

By 1920, the US had a string of 12 coastal stations stretched along the Atlantic seaboard from Bar Harbor, Maine to Cape May, New Jersey.

During World War I amplitude modulation was developed, and in the 1920s spark radiotelegraphy equipment was replaced by vacuum tube radiotelephony allowing voice communication.

Also in the 1920s, the ionospheric skip or skywave phenomenon was discovered, which allowed lower power vacuum tube transmitters operating in the shortwave bands to communicate at long distances.

Hoping to foil German detection during the World War II Battle of the Atlantic, American and British convoy escorts used Talk-Between-Ships (TBS) radios operating on VHF.

A few portable VHFs are even approved to be used as emergency radios in environments requiring intrinsically safe equipment (e.g. gas tankers, oil rigs, etc.).

AIS data is carried on dedicated VHF channels 87B and 88B at a baud rate of 9,600bit/s using GMSK modulation[4] and uses a form of time-division multiplexing.

A marine VHF set is a combined transmitter and receiver and only operates on standard, international frequencies known as channels.

Transmission power ranges between 1 and 25 watts, giving a maximum range of up to about 60 nautical miles (111 km) between aerials mounted on tall ships and hills, and 5 nautical miles (9 km; 6 mi) between aerials mounted on small boats at sea level.

[7] Full duplex channels can be used to place calls over the public telephone network for a fee via a marine operator.

These international conventions include: Slightly adjusted regulations can apply for inland shipping, such as the Basel rules (de:Regionale Vereinbarung über den Binnenschifffahrtsfunk) in Western Europe.

In 2022, the ETSI issued a proposal for implementing the use of FDMA protocols on the band in response to increasingly scarce availability of voice channels in some circumstances owing to the widespread use of systems such as AIS.