NAVTEX Filtered to Two Categories
On the second day of a five-day coastal delivery you take over as skipper of a 24 m charter vessel. The NAVTEX receiver (518 kHz and 490 kHz, with a printer) has been set by the mate as follows: message categories 01 and 05 only, "to save paper"; 490 kHz disabled, because "we don't read the local language"; station selection limited to the two stations of your home area. The paper roll ran out at about 03:00 and the alarm was muted at the same time. At 09:00 you find from the printed log that a gale warning and a search-and-rescue message for a missing yacht 30 nm ahead were broadcast overnight. The forecast app on your phone shows a different wind strength from the last printed forecast. The next leg takes you 60 nm along the coast, crossing two NAVTEX coverage areas.
1. Which of the mate's settings do you keep and which do you change?
Read the worked answer
Change them all.
NAVTEX is an MSI receiver, not an entertainment filter. Categories 01 (navigational warning), 02 (meteorological warning) and 04 (search-and-rescue information) are exactly the messages that must never be filtered out, and on many sets they cannot be. Category 05 (meteorological forecast) is routine but you need it. A setting of "01 and 05 only" removed the two messages that could have changed your plan overnight - a gale warning and an SAR broadcast about a yacht 30 nm ahead.
Actions: print all categories in use (at minimum 01, 02, 03 if ice is relevant, 04, 05); reload paper; unmute the alarm; and restore station selection to cover both areas you will cross, because coverage areas in the NAVTEX Master Plan each have their own station and schedule. A silent printer is not a quiet radio - it is a receiver that has stopped telling you things.
2. What are 490 kHz and 4209.5 kHz for, and does disabling them matter?
Read the worked answer
518 kHz is the international, English-language NAVTEX service, and it is what the carriage requirement is essentially about.
490 kHz carries national-language broadcasts, typically for inshore and local waters. 4209.5 kHz is used in tropical waters where MF propagation on 518 kHz is unreliable; the Master Plan states where and when.
Disabling them does not breach the international requirement, but it can remove local hazard warnings - a buoy adrift, a dredging area, a firing range - that are never repeated in English on 518 kHz. That matters most close inshore, which is where you are.
If nobody aboard reads the language, the correct fix is a crew member who does, or a reliable translation route, not switching the receiver off. Check the Master Plan for which stations broadcast on which frequency in the two areas you are about to cross, and set the receiver accordingly.
3. What do you do about the missed messages, and how do you satisfy yourself that you have the full MSI picture for the next two days?
Read the worked answer
- Recover what you can. Most receivers store received messages; check the store and the printed log for times of origin. NAVTEX messages are repeated at the station's subsequent scheduled transmissions until cancelled or superseded, so the gale warning and the SAR message will very likely come round again within the 4-hour cycle.
- Read the time of origin. Do not act on a stale forecast; a gale warning cancelled two hours ago is not a gale warning.
- Fill the gap by other means - the coast station on VHF, the RCC for the SAR message, or an approved MSI source - and log what you obtained and when.
- Restore the receiver (paper, alarm, categories, stations) and confirm it is actually printing by watching the next scheduled broadcast.
- Treat the phone app as a cross-check, not as the MSI source. It is not approved, and it disagrees with the last printed forecast anyway - which is itself a reason to get an authoritative one.