Sunday, 2 September 2018

FT8 and callsign extensions.

I had a lovely couple of hours down at the seaside again this afternoon, in time for high tide - and lots of Russian, Japanese, and even an Argentinian QSO - all on just 15W and a mobile stick!

I also understood a small problem that was occurring with WSJT-X in FT8 mode.  Sometimes, I noticed that, in response to a caller, my reply would be 'de MW1CFN/M -08', which understandably left the caller unsure who I was calling back!

After a few cycles of this, I realised that what was happening was the caller sending a signal report as his first contact, and not his Maidenhead locator.  This sends the auto sequencing into this callsign-free reply. This only happens when the callsign has an extension such as /M or /P, presumably because the extra two characters make sticking another callsign into the message exceed the message limit.

Everyone who sends their grid locator first is rewarded with a fault-free sequence of transmissions.  The sequence calls CQ with a /M first, then answers with only the normal call, without the /M.  It finishes with a 'de MW1CFN/M 73', by which time the other caller is happy enough to accept it, and the logging within WSJT-X correctly records each callsign.

I'm just glad my best two JA contacts did things properly, and were duly confirmed.


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