From Bud:
DS2072A Hardware v2.0, Firmware 00.03.00.SP1
F=280MHz via a 280MHz bandpass filter to reduce source spurious/harmonics
..
These look like there might be a tiny bit of 200kHz modulation in the clock. But I'm also noticing the close-ups of the main carrier show that there is a slight difference in the offset between the two sources which may imply it's in the source.
I'm undecided on this one.
Bud: Being a precision RF guy, you probably know these sources very well. Your comments? Have you looked at your Rigol's internal clock with a swept analyzer?
No I still have not opened my scope, not sure yet if to sell it as there are many little things, beside possible clock issues, that irritate me and create a perception of a Fisher-Price product (you folks who do not know who Fisher-Price is can look ip the name in Wiki). To name a few :
- the elusive 50 Ohm input issue when the inputs forget their 50 Ohm state on power up so the settings say they are on 50 Ohm when in fact they are not
- deactivation of measurements is awkward and done with separate buttons than activation
- saving waveforms all of a sudden the filenames switch to Chinese with no option to switch to English
- tiny fonts in measurements
- lock ups when in setting internal date/time
- lock ups when the scope is connected to LAN
- cumulative lock ups even with the scope not connected to LAN nor to USB but if it locked up once, it locks up again after a few min after a reboot, then keeps locking up with a smaller and smaller interval after each reboot until locks up almost instantly after reboot. This I found to be specific when the scope is configured to boot to the Last state vs Default state. The way to fix it was to set the scope in the menu to boot to Default state, which seemed to clear the memory that stores the current corrupted settings or whatever, so the scope ran ok after booting to Default state. I now configured it again for Last state and so far so good but I feel that is again until something happens that will cause it to lock up and then again after each reboot it may have that issue.
I am too busy to leave with the above problems, I want to have an Instrument that I turn on and it works and I trust it. Cant say so about DS2072A.
But anyway , getting back to the waveforms. I do have a problem with the 100/200kHz peaks that seem to be PFD artefacts but they look too strong, being only 60dB down from the fundamental. Especially the 200kHz one. THis may indicate the loop filter sucks as it supposed to suppress these artefacts that are way away from the loop filter cut-off frequency of about 3kHz.
Also I am worried what that 60kHz artifact is (the closest to the fundamental). It is only 45dB down which is pretty bad. Its origin is unknown but does not seem to come from the source as I used two different sources. So yes I feel like clock on DS2072a also should be checked with a spectrum analyzer.