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KiwiSDR GPS frequency correction issues resolved - new advice if using an external GPSDO is to set to 66.66 MHz
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Gwyn Griffiths
John Seamons issued a fix in v1.557 for the absence of GPS frequency corrections when there were no browser connections.
The problem was outlined in post https://groups.io/g/wsprdaemon/topic/kiwisdr_gps_frequency/93331251 That fixed has worked well. So well that it led to attributing the source of a "1 Hz offset" between some KiwiSDR users using GPSDOs set to 66.6 MHz and the now well-corrected Kiwis. The error is due to the fixed frequency relationship between the clock frequency and the 12 kHz audio sampling rate. John Seamons has provided a description at https://forum.kiwisdr.com/index.php?p=/discussion/2721/external-clock-frequency-compensation-not-fully-applied#latest Exact 12 kHz audio sampling rate is possible if the External clock frequency is set to 66.66 MHz. This is now suggested best practice. KiwiSDRs using their own GPS frequency corrections after v1.557 update will be 0.1 Hz different at WSPR baseband frequencies because the internal clock is a nominal 66.6666 MHz. Gwyn G3ZIL |
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WA2TP - Tom
This seems to suggest that while using an external clk gpsdo like the bodnar, it should be set to 66.66. Currently I have mine set to 66.6666.
On Sep 5, 2022, at 4:34 AM, Gwyn Griffiths via groups.io <gxgriffiths@...> wrote:
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Glenn Elmore
Yes, that's probably optimum for frequency accuracy and plenty good with Bodnar's for purity. I'm not even certain that more digits would make measurable degradation as a Kiwi clock. The Bodnars use Si5328's which have microwave VCOs rather than sub 1 GHz ones like the Si5351. This gets one another 14 dB ( or something) suppression of spurious. I had a quick look last night at a Bodnar Mini and I don't think it really matters much what you use so 66.660 MHz is a good choice if it buys zero frequency error.
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I had to use the 5351 instead of the 5328 in the Kiwi frequency extender and the (subset) Reference board ( 'poor mans Bodnar') because of parts availability and ~ 1 year times. Cost is quite different too. On 9/5/22 07:43, WA2TP - Tom wrote:
This seems to suggest that while using an external clk gpsdo like the bodnar, it should be set to 66.66. Currently I have mine set to 66.6666. |
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Rob Robinett
In my next WD build I will employ kiwirecorder's --resample option to improve frequency accuracy and spectral purity of Kiw's which use the internal GPS services On Mon, Sep 5, 2022 at 5:10 AM Glenn Elmore <n6gn@...> wrote: Yes, that's probably optimum for frequency accuracy and plenty good with --
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