External clock frequency compensation not fully applied
Following the update in v1.557 that fixed the GPS frequency aiding problem when only using kiwirecorder.py we have been able to document what looks like incomplete compensation for the user-set frequency for an external clock in the Config panel.
Entering the external clock value in the box does set the correct RF frequency, i.e. using IQ display at 10.000000 MHz there is only jitter receiving a 10 MHz external standard. This happens correctly even if, say, the external clock and entry in Config screen is at 66.600000 MHz.
However, but there appears to be a second, baseband clock correction that does not get done. Why baseband? Because the offset we see is constant irrespective of RF frequency. It appears as if baseband processing assumes the clock frequency is 66.666600 MHz irrespective of what's in the Config box. With 66.600000 MHz input frequency and Config example, the external clock is 0.1 percent lower than 66.666600 MHz, that is, 1.5 Hz in 1500 Hz. 1.5 Hz is the offset that we see at 1500 Hz baseband frequency, i.e. dial frequency of 9998.5 kHz and USB mode for a 10 MHz input.
Setting the external clock to 66.666600 gives a match to within 0.1 Hz of expected.