FT8 protocol question: F/H DX operation

I'm hoping someone here can answer a question I have about the FT8 protocol.

While monitoring a DXpedition using fox/hound mode (F/H) I observed the fox (H44WA, Solomon Islands) sending occasional FT8 "free text" messages that I have not seen before. I'm wondering if someone can tell me what these are. I did a bunch of Googling and even looked at the source code to MSHV, but couldn't find any explanation.

Look at the image below. You can see the hounds calling above followed by the fox acknowledgements below. One in standard message format (msg = 1.0), a report to 4Z5PJ. Then a DX message format (msg = 0.1) with an RR73 to HL5QY and a report to HK30.

But then there is this third message in free text format (msg = 0.0) that has the fox's call and a 6-digit number. These are not sent on each fox exchange. Only occasionally. And the number usually increments by a large random amount (10's to 100's of thousands), but not always.

Does this have something to do with an associated logging program? The number value is too random to be some sort of logging serial number.


  • Ha! Thanks for that. This is interesting because during the Bouvet 3Y0J operation, where there was considerable piracy, I had also thought about what FT8-based anti-spoofing methods might be implemented.

    Although the H44WA method certainly helps I don't believe it's secure against simultaneous pirate operation. It only guarantees H44WA was active during the time slot. It doesn't guarantee the specific QSO occurred with H44WA.

  • A coupla nights ago I saw the opposite: a VR that's line-of-sight to me worked one of the current DXpeditions on 1.8 Mc. Then a coupla minutes later QSYed a few hundred cycles & worked the DX again with the callsign of an EU country-of-origin mate of his... noticeably earlier than the advance of the descending earth turn made it possible for the DX to work real EU stations.

    Recently in JT-mode chatter, there was somebody down VK/ZL way calling for adding something for call verification to WSJT-X as somebody had been bootlegging his call - NOT a VK9/0 or greater-than-or-equal-to ZL7.

    Seems everybody wants WSJT-X to be something a bit like an Orgasmatron (what next, a Don Miller/Romeo Vega-Roman Stepanenko detector? ;^). Used to be that we did radio on the radio. And the operator had something to do with doing the operating.

    73, VR2BloodyGeezer.

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