Oh this is turning into an interesting learning experience
![Huh? ???](https://www.eevblog.com/forum/Smileys/default/xhuh.gif.pagespeed.ic.6Nvt7O8a11.png)
Here's some experiments and what I think they mean:
First, I switched out the probes. Instead of the supplied Rigol 150MHz probe, I used a 250MHz probe (Coline M12W). I carefully adjusted both matching pots according to the directions. I realize that this is not fair, given that the purpose of this was to test the system supplied by Rigol as a whole, but thought it might make a difference. I also selected "Dots" and turned on persistence. Here is the result:
![](http://www.picturehosting.verhey.org/rigol/dots250.bmp)
You can see the calculated rise time is just about the same as before. Notice that the line is a touch thick in places -- my circuit is still on the breadboard which I *think* is the cause of the jitter.
But WAIT! If we change the time base to 5ns, something interesting happens:
![](http://www.picturehosting.verhey.org/rigol/dots250b.bmp)
WTF!!!
While in both cases, the leading edge of the pulse is clearly shown, in the 5ns shot, the *trailing* edge has dropped further back to 0. Using the manual cursors, It appears that the Rigol is using the displayed trailing edge when determining the minimum voltage for the rise-time calculation, NOT the displayed leading edge. I don't think this is the right way to do it. Correct me if I'm wrong, but rise time should be looking at the pre-trigger minimum, not the post-trigger minimum, should it not?
With that thought in mind, I used the manual cursors to carefully plot the 10% and 90% points, flipping back and forth between X and Y displays to ensure the points coincided:
![](http://www.picturehosting.verhey.org/rigol/dots250c.bmp)
And now, back to the original Rigol 150MHz probe for a manual measurement:
![](http://www.picturehosting.verhey.org/rigol/dots150.bmp)
So, allowing for manual error and the fudge factor caused by the jitter in my circuit, I think it's fair to say the rise time is 2.5ns +/- .06ns? Which suggests a Gaussian bandwidth of 3.4\2.5*1000 = 136MHz?
EDIT: Forgot two things: first, thanks to tnt and alm for teaching me not to trust the automatic measurements. And second, this seems to confirm that telling the scope it's now a 150MHz DS1152E-EDU model means bumpkiss. Once the input filter is defeated with the 100MHz mod, that's all you get. Anything more requires a hardware mod, if it's possible at all.