By: Katie Power

Inventors It is unsure who invented the Marine VHF Radiotelephone.

Who/What Uses the Device Ships use this device, for example the navies, the coast guards, cruise ships, and fishing vessels.

All about the VHF Radiotelephone This is the frequency range between and MHz. It's installed on all large ships. It is also used on rivers and lakes. It is used for a lot of purposes like summoning rescue services and communicating with harbours and bridges. Also, it is used for collision avoidance. A marine VHF set is a combined transmitter and receiver and only operates on international frequencies known as channels. Frequency Modulation (FM) is when antennas have to be vertical in order to have good reception to use it.

How Does A VHF Radiotelephone Work? Modern-day marine VHF radios not only offer basic transmit and receive capabilities. Permanently mounted marine VHF radios on seagoing vessels are required to have certification of some level of "Digital Selective Calling" capability, to allow a distress signal to be sent with a single button press. Marine VHF mostly uses "simplex" transmission, where communication can only take place in one direction at a time. A transmit button on the set or microphone determines whether it is operating as a transmitter or a receiver.

Evolution of the VHF Radiotelephone Modern-day marine VHF radios not only offer basic transmit and receive capabilities. Permanently mounted marine VHF radios on seagoing vessels are required to have certification of some level of "Digital Selective Calling" capability, to allow a distress signal to be sent with a single button press. Marine radio was first installed on ships around the turn of the 20th century. In those early days, radio (or "wireless" as it was known) was used primarily for transmission and reception of passenger telegrams. Radio watchkeeping hours were not standardised, and and there was no regulatory requirement for carriage of radio by ships. Indeed, there was a general lack of regulation of the radio spectrum. Amateur/experimental stations often interfered with commercial stations and vice-versa.

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