NAVTEX

NAVTEX (Navigational Telex) is an international automated system for broadcasting Maritime Safety Information (MSI) to ships using narrow-band direct-printing (NBDP) radio telegraphy. The primary international frequency is 518 kHz, used for English-language broadcasts; 490 kHz is used for national-language broadcasts; and 4209.5 kHz serves tropical or long-range coastal areas where 518 kHz propagation is poor. Broadcasts originate from co-ordinated shore stations and cover a radius of approximately 200–400 nautical miles. Each NAVTEX transmission begins with a four-character header identifying the transmitter by a letter designator (B1), the subject indicator (B2), and a two-digit serial number (B3–B4). Receivers are programmed by the mariner to accept specific station/subject combinations, suppressing repeat messages and irrelevant broadcasts. Subject categories include navigational warnings (A), meteorological warnings (B), ice reports (C), SAR information (D), and meteorological forecasts (E), among others. NAVTEX watch-keeping is required by SOLAS Chapter IV, Regulation 7, for vessels in Sea Areas A1 and A2. IMO Resolution A.617(15) established the original NAVTEX Performance Standards; these were subsequently refined through amendments. The Co-ordinated Universal Time (UTC) transmission schedule prevents interference between adjacent stations broadcasting on the same frequency.