Successful Navtex reception

[Mike Brown]

Hi Alan

I had some success receiving Navtex this evening, despite not having a sensible antenna and being well inland. Antena was a 10m vertical via an untuned HF-only auto-atu. RX was my HL2. There appear to be a number of different transmitters taking turns to transmit. Some in the UK, others appeared to be from France, Belgium, Holland and possibly Ireland.

Comments:

I haven't tried receiving Navtex before - some comments may be due to my ignorance rather than your software!

Overall Navtex is a great new feature. In just an hour or so I've seen some really interesting warnings such as undersea obstructions, unlit oil platforms with broken foghorns, wind turbines with broken foghorns,  gale warnings etc.

I needed to tune to 517 kHz instead of 518. R4 LW is spot on at 198 kHz, so it isn't an SDR frequency-offset issue.

I haven't so far seen any signals on 490 kHz.

The text window appears as though it may need word wrap - one line I saw ran off the side so was truncated (maybe there was a lost LF/CR but it would be better to wrap than lose text.) 

The text scrolls down as the message is received but can be really odd. In the screenshot attached, there are three blocks of text, all part of the same message but in reverse order. It looks as though the software thinks a new message is being received part way through one and restarts at the top. Possibly corruption due to QSB/QRM? Suggest not restarting unless ZCZC (start of message) or NNNN (end of message) are received. 

Random characters can be generated from noise when there's no transmission present, so squelch might be useful. 

The text window buffer is a bit short - random characters from noise can mean a successful decode disappears off the bottom. 

Scroll bar operation is a bit odd and it can keep jumping to the top - possibly as new noise-generated characters appear at the top? A stop or pause reception button might be useful.

 

Hope the information is useful/interesting.

73

Mike

G4RAA

[ahop...@googlemail.com]

Hi Mike,

thanks very much for the feedback, all very useful and great to see it is decoding real messages. It really was not ready for release but I forgot to hide it before releasing the crash fix. I'm thinking of adding other marine modes like AIS and weatherfax as a means to combine hobbies and give myself a bit more spark motivation.

73 Alan M0NNB