Do you get the same effect when scanning the lower frequency range?
I think also you may have found a bug.? Tracking and spur reduction should not work in the high range, only the low range.? It is quite possible there is some effect going on here - what happens if tracking is turned off?? I think you may have to go to low range, turn it off, then back to high range.
It could also be harmonics from the 30MHz oscillator signals if they are not carefully routed away from signal paths and kept short.? Unfortunately I am away from home with just company laptop, which is locked down to some extent, so I am not able to install kiCAD and view your layout at the moment.
The mixer, LO and SAW filters are not used at all in the High range - it is just a signal into the SI5531, filtering is mainly done in the SI5531 internal DSP.
My guess is some of the 30MHz clock is getting into the signal path, or possibly there is a bug and even though the Ref output is shown as off maybe it is not.? That would need some testing.
Your noise floor is around 10dB lower than my one, which is good.
Dave
