Question 3-88N4

NAVTEX is an automated system for broadcasting Maritime Safety Information (MSI) to ships. It is a one-way broadcast service, meaning ship stations only receive the information. * **A) Receives MSI broadcasts using SITOR-B or FEC mode.** This statement is **correct**. NAVTEX specifically uses the SITOR-B (Simplex Teletype Over Radio, Mode B) protocol, also known as FEC (Forward Error Correction). FEC is ideal for broadcast services as it adds redundant data, allowing the receiver to correct errors without needing a return channel for acknowledgements or retransmissions. * **B) The ship station transmits on 518 kHz.** This is incorrect. Ship stations do not transmit NAVTEX messages; they only receive them. 518 kHz is the primary international frequency for shore stations to *broadcast* NAVTEX messages. * **C) The ship receives MSI broadcasts using SITOR-A or ARQ mode.** This is incorrect. SITOR-A (ARQ - Automatic Repeat Request) is a two-way, error-correcting mode where the receiver requests retransmission of corrupted data. This is unsuitable for a one-way broadcast system like NAVTEX, which uses SITOR-B (FEC). * **D) NAVTEX is received on 2182 kHz using SSB.** This is incorrect. NAVTEX broadcasts are primarily received on 518 kHz (international) and 490 kHz (national/local), using a digital mode (SITOR-B/FEC), not Single Sideband (SSB) voice. 2182 kHz is the international distress and calling frequency for radiotelephony (voice) using SSB.