[...] but I do not know the offset of my sound card clock; my sound card clock and my low-accuracy reference clock differ by 0.3Hz (+/- 1mHz over short and long time intervals), so until install an accurate clock I can only guess that my clock offset could be +/-1Hz or so. Accordingly the center frequency of the signal shown here could be +/- 1Hz or so from the indicated 8972.81

Is it most likely that the signal in the attached is QRM?