10. Communication at Sea (Part II).

6. Radio

In 1901 an Italian inventor named Marchese Guglielmo Marconi transmitted a radio signal across the Atlantic Ocean, and by 1910 the United States had passed a law requiring its passenger ships to have radio equipment on board. Radio made it possible, for the first time, for a vessel out of sight of land or other vessels to keep in touch with the rest of the world.

8. VHF

9. 

Today there are two basic kinds of radios found aboard ocean-going vessels. Marine VHF (very high frequency) radios require an uninterrupted line of sight between antennas. This limits their range, and they are usually used to communicate over small distances. Most marine radio traffic occurs over VHF radio, since skippers are naturally most concerned about vessels, port facilities, and hazards in their immediate vicinity.

Marine VHF Radios are two-way communicators which are used to transfer and receive messages. However, the most important function of a Marine VHF Radio is that it is very helpful when it comes to sending distress signals across the channels to coast guards and other ships and boats in the periphery. Another important aspect of Marine VHF Radios is the fact that they come in two main categories: portable ones and non-portable ones. The portable ones have waterproof coverings and are battery operated in order to facilitate the power transmission. The fixed or the non-portable Marine VHF Radios cover a lot of aerial ground, their source of power transmission and energy, huger in comparison to their portable counterparts and are therefore far more feasible in terms of their operational facilities.

11. Satellite communication

Satellite communication is a relatively new alternative for long-distance communication. It features many advantages over conventional point-to-point radio. Instead of transmitting an analog signal directly from the vessel to a shore station, a digital signal is transmitted upward to a satellite. The satellite then relays the signal to another satellite or to a receiver elsewhere on the surface of the earth.

Satellite communication is private. When you use VHF, everybody with a receiver in range can monitor your conversation. Signals transmitted for satellite communication, however, are highly directional, making them much more difficult for the casual eavesdropper to pick up. Satellite communication allows direct access to the global communication infrastructure (telephone and computer networks).

Satellite communication is not greatly affected by atmospheric or meteorological conditions.

Inmarsat system

Satellite services, as opposed to terrestrial communication systems, need the help of geo-stationary satellites for transmitting and receiving signals, where the range of shore stations cannot reach. These marine communication services are provided by INMARSAT (a commercial company) and COSPAS – SARSAT (a multi-national government funded agency).

Inmarsat, or International Maritime Satellite, is an international partnership of government and private entities representing 75 countries. Headquartered in London, its charter is to provide mobile satellite communication services to the world. Inmarsat was established in 1979 and began providing services in 1982. Currently, Inmarsat uses four of its own satellites and leases maritime communication capacity on several other satellites.

While INMARSAT gives the scope of two way communications, the COSPAS – SARSAT has a system that is limited to reception of signals from emergency position and places with no facilities of two way marine communications, indicating radio beacons (EPIRB).

Communications within the ship

Communications within the ship are done by an internal telephone system. Communications over relatively short distances can be made by visual or sound signals. Visual signals can be sent by using an Aldis lamp (an Aldis lamp is an electric lamp used for flashing messages in Morse Code.) Sound signals can be made with the ship’s siren, whistle or bell. In emergencies, rockets and flares are used to signal distress and to acknowledge such signals.