Another plot from Wolf's receiver at Bielefeld,
This covers the full transmission from 22:30 UT in 50.5 uHz
bandwidth. The line at 8820.0000 is 11.7 dB above the
noise in this 1980 bin span.
It is the strongest bin in +/- 0.5Hz (19800 bins).
Of course, I also checked nearby integer frequencies - when using
PPS GPS timing there is the possibility of weak harmonics from
the timing system.
I tried Cumiana with this narrower bandwidth but no improvement.