NAVTEX is an international automated direct-printing for promulgation of Navigational & Meteorological warning and urgent information to vessel. The information transmitted by NAVTEX maybe relevant to all sizes and types of Vessel and the selective message-rejection feauture ensures that every Mariner can receive a safety information broadcast whish is tailor to his particular needs.
NAVTEX means the system for the broadcast & automatic reception MSI by means narow-band direct-printing Telegraphy. International NAVTEX service means the co-ordinated broadcast and aotomatic reception on the frequensi 518 kHz of MSI by means of narow-band direct-printing Telegraphy using English language. National NAVTEX service means the system for the broadcast & automatic reception MSI by means narow-band direct-printing Telegraphy using frequencies other than 518 kHz and other National language. This service may simply repeat the messages broadcast over the International NAVTEX service but in the National language, or they may be tailored to meet particular National requirements, for example by providing different or additional information to that broadcast on the international NAVTEX service targeted at recreational Vessels or fishing fleet. This NAVTEX service may be boradcast on 490 kHz or 4209-5 kHz (frequencies co-ordinated by IMO through the NAVTEX Co-ordinating Panel) or on National assigned frequency.
Introduction NAVTEX Reception: Users should be aware that where there is a significant overland path between the transmitter site and the user, the strength of the signal will be markedly reduced as will the range at will the signal maybe receiped. Furthermore the topography of ports and harbours and the presence of high rise building may distort or preclude reception of NAVTEX.
Principal features of NAVTEX: The International NAVTEX service uses a single frequency with transmission from nominated stations within each NAVAREA / METAREA, arrange on a time-sharing basis to reduce the risk of mutual interference. All necessary information is contained in each Transmisson. A dedicated NAVTEX receiver which has the ability to select messages to be printed, according to: a. a technical code (B1B2B3B4), which appear in the preamble of each message; b. whether or not the particular message has alredy been printed.
Message Priorities: Three message priorities are used to dictate a timing of the first broadcast of a new warning in the NAVTEX service. in descending order of urgen they are: VITAL : for immediate broadcast, subject to avoiding interference to ongoing transmisson; IMPOTANT : for broadcast at next available period when the frequency is unused; ROUNTINE : for broadcast at next schedule transmission period.
NOTE: both VITAL and IMPORTANT warnings will normaly be repated, if still valid, at the next schedule transmission period.