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NAVTEX - Story
NAVTEX is the direct successor of the former manual managed information and alerting system in
maritime mobile service. Navigational Telex is a narrow band direct printing system (NDBP) on
medium wave frequencies ( 518, 490 kHz) for delivery of navigational and meteorological warnings
and forecasts, as well as urgent marine safety information to ships. It was developed to provide
a low-cost, simple and automated means of receiving this information aboard ships at sea within
approximately 300 nautical miles of shore.
There are no user fees associated with receiving NAVTEX broadcasts.
NAVTEX is a component of the International Maritime Organization/International Hydrographic
Organization Worldwide Navigation Warning Service (WWNWS). NAVTEX is also a major element of the
Global Maritime Distress Safety System (GMDSS). International Convention for the Safety of Life at Sea
(SOLAS) mandated certain classes of vessels must carry NAVTEX, beginning August 1, 1993.
In the transmitting scheme of NAVTEX are 10 minutes time slots for each station to transmit its
information with a repetion period of 4 hours. This normaly equals to the working shifts of
mariners on board of ships. With a transmitting rate of 100 Baudot one can transmit 8000
characters per timeslot. Because of double transmitting each letter only 4000 characters
are available. This is equal to 65 lines text with 60 characters per line, or one page of office paper.
Some national agencies want to extend NAVTEX service significantly. There is a 'need' for more
information to transmit in a more modern system. Investements on new equippment becomes
necessary to take part in this service ashore and on board of all concerned ships.
Is this service necessary and must it be transmitted on 500 kHz ?
Answer 1:
When checking the present navigational telex broadcasts one can find not a few reports which are
not of that importance to been broadcast on a 300 miles area coverage. E.G. 'Lost anchor chain on
road etc with postions etc' are only of interest for mariners intending to go that place. All others
would not care on this message. It is only worth of being mentioned in a new kind of 'local' or
'sectional' navtex system on vhf channels to be build by the authorities on a 'text to speech'
system and perhaps telex broadcast for printout.
Answer 2:
'Coastal rumor' reports test transmissions by French agency Corsen on 500 kHz for NAVTEX
purposes. There is no technical nor administrativ reason a new NAVTEX could only be sent
on 500 kHz. Out of the spectrum there are other frequencies (512kHz) available for transmit.
So national agencies might join the proposals of former radio officers to give the '500 kHz'
a special opportunity to become a UNESCO immaterial cultural heritage.
500 kHz for UNESCO intangible heritage
Read NAVTEX story in
Wikipedia in several languages
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