Stefan,
My stable/accurate time reference (GPSDO) should arrive in two weeks; in the meantime I am hoping to use 11904.76190 Hz (per your suggestion, thanks) to assess my soundcard clock frequency offset. I have been guessing (based on comparison with another uncalibrated but stable oscillator) that the frequency offset of my soundcard gives less than 1Hz error at 11904.76190 kHz.
I have attached a screenshot captured over the last 24 hours, showing a modulated signal centered at an indicated frequency (red marker) of 11905.1884 which would have a 0.426 Hz offset from 11904.76190 Hz.
The signal seems to be fading about 40dB on a 24-hour cycle, with a minimum at ~ 2000 UT (clock times in my screen capture are Arizona time, UT – 7 hours).
Could the modulated signal shown here be the 11904.76190 Hz signal?
73, Jim AA5BW
