Hi Cncjerry,
thank you for the hints, trust me, I already tried every setting possible to minimize it.
As I wrote before, Rigol support already confirmed that
this problem is present in all their units and that they can't find a solution. They explained that at the frequency of 10.000 Mhz something happens because of the TG design and is hardware related and this is why they can't find a solution with the firmware. Maybe in the future they change again their hardware but for now they didn't gave me any hope.
This is why I ask if others can check the hardware/firmware and make the test to confirm if the problem is present or not.
I don't know but maybe the same "glitch" is on other frequencies and because it's visible only with narrow filter settings it's hard to find it in 1,5 GHz band sweep.
It's just because I had to build a 10 MHz filter that I found the anomaly in the response trace. You know.... when you are so lucky......you find a needle in a haystack
Thank you