Is the signal in the attached most likely QRM?
The amplitude has varied by only +/-5dB over a 24 hour period*, which makes me think that the signal is local (QRM).
The two frequencies exhibited by this signal are 12mHz apart, and stable within the < 1mHz stability of my sound card oscillator. It is the 12mHz frequency shift, sustained over a 24 hour period, that makes me wonder if the signal is something other than QRM.
Regarding uncertainty of absolute frequency: the signal is shown near 8972.81 Hz, 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
At the moment I have only one antenna, pointed east-west [toward Tom(dj8)CAT et al], so I can’t rotate to see if the signal looks like a (distant) point source.
Is it most likely that the signal in the attached is QRM?
73, Jim AA5BW
* +/-5dB over a 24 hour period with ~45 minute integration time – 358uHz FFT bin width
