Tuesday, 13 August 2013

NAVTEX 518 kHz

At regular intervals on 518 kHz NAVTEX messages are transmitted by various coast stations.
NAVTEX stands for (NAVigational TEXt messages). This radiotelex service transmits navigation and meteo warnings and Search and Rescue messages. 

Of course you can use a dedicated NAVTEX receiver but if you have a general receiver that can be tuned to 518 kHz in SSB, than you can receive and decode NAVTEX messages.




My FT450 is capable of receiving this frequency. I used a simple magnetic loop antenna

made of 11 turns of wiring around 4 nails inside the attic roof.  This antenna using a 150 pF variable capacitor is capable of receiving 470-520 kHz (includes the 600 m ham band).

NAVTEX uses the AMTOR FEC mode. This code is supported by MultiPSK.




The NAVTEX coast stations not too far from my QTH could be received and decoded (Oostende, Dutch coastguard).  In the UK, Grimeton there is also a NAVTEX transmitter.
The coaststations transmit in a tight schedule,  every 10 minutes another station takes over the transmission.

More info;

http://www.scannernet.nl/navtex/info-navtex.html

http://nl.wikipedia.org/wiki/Navtex


Also, find below the comments of Jan, PA3ABK with tips for additonal software capable of decoding NAVTEX information/signals.

4 comments:

  1. Altough MultiPSK is a good program to decode NAVTEX, it doesn't do much more than that. In general the content of NAVTEX is not much of interest for hamradio. It's more the skill to receive the long range stations. One of the programs which fullfills this is Yand. Apart it can receive NAVTEX msg's, the signal will be analysed and this data is stored in a database. The decoder is in one word superb. Especially when the calibrationroutine is performed. An overnite run in NL will sometimes result in unexpected longrange reception. Singapore, Egypte US Canada even with a simple means are no exception.
    The program is able to identify the transmitter with the aid of a database and needs only some "keywords" to define it's ID, even tough the msg looks garbled.
    The disadavantage of NAVTEX is, that all stations are on one freq, for longrange transmission slots are likely to overlap. However you will be amazed how Yand will stay synced under these severe conditions.
    Visit the website for more: http://www.yand.wavetalk.org/

    Frisnit is another application but generates less info about the quality. It connects to a internet database so others can read the msg received. It's like the many amateur weatherstations reporting on the internet. The decoder is also very good.
    For those experimenting on MF, NAVTEX transmissions are a valuable source of propagation data.

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  2. Dank voor je aanvullende info Jan. Ik ga die programma's zeker eens proberen, had er nog niet van gehoord.

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  3. small correction to the above,
    Grimeton is in Sweden, not in UK. worth a visit if you ever visit scandinavia,

    I enjoy reading your blog

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  4. Thanks for your input ! Tack

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