I had this for a long time in my TODO list: the Power Meter function gave wrong results compared to my Siglent SSA3021X and obviously I was doing something wrong.
So I studied how the Channel Power is determined and adjusted the routine, accordingly. There was a bug with the frequency handling, as well, which I corrected.
The results? See for yourself:
This pictures shows my local DVB-T transponder, measured with the Siglent SSA3021X: