GPS frequency correction not being applied if only connections present

As part of investigations into the use of FST4W on the HF bands, in conjunction with WsprDaemon, we have come across an issue.

If connections are the only ones to a KiwiSDR (tested with versions v1.498 and v1.554) then the GPS derived frequency corrections do not take place. Rather, the frequency drifts. The issue and a workaround are described in detail in the attached pdf.

Immediately on opening a browser connection to the Kiwi - it can be admin or a receiver channel - the GPS corrections resume. GPS corrections continue so long as the browser window is active. If it suspends then the corrections do not happen until it is reloaded.

This provides a workaround - keep a browser connection open to the Kiwi.

With this knowledge, we are reevaluating our previous measurements of spectral spread as they may have been influenced by unnoticed drift.




  • Yep. It's a long story, but basically the clock correction code was developed years before kiwirecorder. And there is an unfortunate interaction such that corrections are occurring, but not being applied to channels when non-Kiwi API connections are the only ones present.

    I'll have a fix out later today or tomorrow. Apologies for this..

  • The very good news is that the Kiwi is exceptionally accurate and stable when the corrections are being applied. For example, on 20M Tom WA2TP's GPS-aided Kiwi_1 is within 0.01 hertz of his Kiwi_7 which is fed by a Bodnar GPSDO.

    We will be upgrading many of the top spotting WSPR stations with your fixed code. I hope having all those sites capable of decoding the longer FST4W modes on the HF bands will encourage more beacon stations to adopt those modes (once they check the stability of their tx oscillators)!

  • Please give v1.557 a try and see if it fixes the observed problem.

  • Thank you, John

    The fix in v1.557 has worked. Over two hours the frequency difference between two updated KiwiSDRs showed an average of 0.09 Hz and an rms difference of 0.14 Hz from 333 measurements.

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