NAVTEX is a system for broadcast and automatic reception of maritime safety and weather information.
NAVTEX is part of the MSI, Maritime safety information, that is broadcast to mariners by official agencies for their safety. Maritime safety messages consist of messages such as weather warning, warnings about dangers to navigation and failure of navigation devices. These messages are broadcast via the Inmarsat satellites, over the Navtex broadcast system and various radio telephone systems as well as the international high frequency narrow band direct printing service. For distributing this information, the world is divided into NAVAREAS where information from official providers is filtered before being broadcast on the system to mariners.
NAVTEX provides ships with navigational and meteorological warnings and urgent information through either on-screen display or automatic printouts from a dedicated receiver. NAVTEX is a component of the IMO/IHO Worldwide Navigational Warning Service (WWNWS) defined by IMO. It is included as an element of the Global Maritime Distress and Safety System (GMDSS).
NAVTEX messages are transmitted worldwide from local stations that provide services targeted at local users and passing ships. Users can set their NAVTEX Receiver to pick up specific message types and reject others. Messages such as navigational and meteorological warnings and search and rescue information are non-rejectable, to ensure that ships are always updated with the most vital information.
Users can choose to receive information from the single transmitter that serves the sea area around their position, or from a number of different transmitters. the Admiralty List of Radio Signals Volume 5 publish a full listing of all Worldwide NAVTEX services and publish regularly updates through the notice to mariners update service.
A NAVTEX transmitting station is operated by an operator who produces a NAVTEX message on his computer, which is transferred to a NAVTEX Transmitter by TCP/IP or other means. The NAVTEX transmitter is connected by a coax cable to an Antenna Tuning Unit, which harmonize the Transmitter frequency to the NAVTEX Antenna.
The distance between the operator and transmitter can be several kilometres, or next door. On long distance, microwave link or fibre optic cable is used for communication.