MFSK32 sync in fldigi

Discussion in 'Working Different Modes' started by W1KU, Feb 4, 2021.

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  1. W1KU

    W1KU Ham Member QRZ Page

    I'm trying to copy MFSK32 traffic in fldigi on HF, and I'm frequently challenged to sync my receive frequency with what is being transmitted.

    Even when an RSID immediately precedes the MFSK transmission and fldigi automatically "tunes" the waterfall to the correct location, sometimes I cannot copy the transmission. Manually hunting for the right frequency via point/click occasionally lets me copy it, but this does not work for unattended reception.

    Any advice? Am I missing a setting in fldigi for more aggressive automatic frequency hunting?


    More info:

    I've had the same problem with MFSK16. MFSK16 images that are received do not appear slanted, which suggests it is not a soundcard calibration issue.

    The problem is intermittent. Sometimes it syncs right away, with or without the RSID. The problem occurs with multiple transmitting stations.

    I'm having this problem with 2 different RX setups :

    1st: RS-HFIQ direct-conversion SDR (tcxo local oscillator) into 192 Kbps EMU-0204 soundcard into HDSDR into "Virtual audio cable" virtual soundcard into fldigi (Windows 10).

    2nd: TS-830s with DFC-230 VFO (1980s era synthesized VFO) into Signalink USB soundcard into fldigi (Windows 10).

    Perhaps the problem with setup #2 is VFO stability, (though the DFC-230 seems OK for my other digital activity and is much more stable than the analog VFO in the TS-830s.

    But I also have the problem with setup #1 which is an entirely digital datapath after the 192 Kbps sampling soundcard. I use the 192 Kbps soundcard in the AARL frequency-measuring-test, and I've tracked stability for hours or days at a time with Spectrum Lab, so I don't think that soundcard is the problem.

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