Monitoring NAVTEX using fldigi

A few days/weeks ago I helped put a navtex receiver on a sailing yacht. I made sure I had it properly filtering through only the stations and messages that were wanted. Later it was obvious that filtering was a bit too tight or something was wrong with the receiver, just one message got through in a week. I started thinking I should listen to Navtex again at home and get a feel for the rhythm of the broadcasts and propagation. I just wanted to know what was on there now before I started to do something about that receiver on the yacht. So, how can I listen to Navtex when I currently have no receiver for it? Well, I have a few options in the junk box. There is the really crappy MFJ-1278 I may still have somewhere. But, that piece of Mighty Fine Junk is so bad that it really would be a waste of energy and I should throw it away or execute it a la the famous printer from the movie Office space. I mean this scene: [Original] Office Space: The Printer Scene
But, I just noticed that fldigi 3.21.49 has added Navtex reception and that could be fun to try out. In the shack I have an almost antique IBM Thinkpad 600x that I have running lubuntu 12.04 and it is still good for experiments like these. So, off to the fldigi website I went and got the latest fldigi binary. When later trying to execute fldigi it complained about a missing libjpeg62.so library and immediately died. So, I launched synaptic, got libjpeg62 and then it worked fine.

I am now running Navtex reception using fldigi, a homemade soundcard interface and get the audio from a Yaesu FT-897. The Yaesu is tuned to 516.50 kHz in USB, fldigi cursor frequency is at 1500 Hz and that has me listening to 518 kHz. A few impressions from using fldigi this way can be summarized as: Navtex reception is quite CPU intensive on the old laptop, fldigi uses about 70 % CPU and that can to a large degree be blamed on the old CPU of the laptop used (P3-600). Fldigi tries to identify the transmitting station by looking at the transmitter "callsign" (it's just a letter) and looking that up in a csv file. By default that file is named incorrectly in fldigi and you need to browse for it in settings. When that file is found then fldigi can log the messages to an Adif file where it spells out the name of the transmitting station (Cullercoats, Niton, Rogaland, Reykjavik etc). That csv file is a very nice idea but it needs some work, at the moment it has the wrong letters in there so it identifies Tallin as Cullercoats etc. I'll see if I can correct that and contribute an improved file. To summarize the experience it was fun to receive Navtex again, fldigi worked reasonably well when decoding the transmissions (it did have some issues with a fading signal but the mode can be like that). I can see some improvements with the obvious bugs and then add filtering of stations and messages. That way I could have the latest weather report available on my server at all times, that leads to other projects... :-)