I still think there must be some way to get your scope to focus on the frequencies of interest. Do you have alternate triggers? For example the Rigol has a "pulse" trigger where one can set the width of a pulse or peak to trigger on.
Or maybe you do need a preamp! Maybe with a stronger signal the scope will concentrate on the larger peaks and ignore the "noise" higher harmonics.
Hi - thanks again for the great suggestions!
However (and being a n00b I'm probably wrong about this, but anyway here goes) - I don't think this is trigger type issue. The existing rising/falling slope trigger works great and in single shot mode already captures the waveform for the entire horizontal duration properly.
I think the issue is what happens
after the capture - there are a lot of harmonics which confuse the automated measurements.
Some scopes apparently make is easy to ignore certain parts of the captured waveforms and measure an arbitrary part of the captured wave. One would
think the R&S RTB2004 would do the same but I guess one would be wrong (this is a $3-4K scope mind you).
This review of another R&S scope on eevblog shows this gating feature (search for "gating"):
https://www.eevblog.com/forum/testgear/rohde-schwarz-rtm3000-review/I also remember reading that the keysight InfiniiVision series (the lower end of which are same price as RTB2004) also do have the gating function for various measurements (among various other features).
Edit: this is available on LeCroy scopes as well, from one of their manuals:
The default starting positions of the measurement gate posts are 0 div and 10 div, which coincide with the left and right edges of the grid, and the First and Last points. Therefore, the measurement gates initially enclose the entire visible acquisition. By moving the measurement gates, you can focus the measurement on the section of the acquisition of greatest interest. For example, if you "gate" six rising edges of a waveform, calculations are performed only on the six pulses bounded by the gate posts.Anyone from R&S reading that can shed a light on this?