Apparently everyone uses auto settings for Sweep, RBW & VBW since no one here has apparently noticed this somewhat severe firmware problem as follows.
This has been reported and confirmed!
To justify my reason to declare this a #1 is this; the need for speed for real time monitoring complex waveforms. Namely ATSC (8VSB) for OTA (Over The Air) broadcast TV for just one example. Many analyzers allow adjusting sweep speeds in manual mode and they stay set no matter what is done otherwise,. But once set, the setting doesn't change (
and shouldn't) if it is in 'Manual' mode.
Knowing that there isn't any free ride, in this case accuracy, something usually has to suffer
which is acceptable in this case since missing changes in the signal for the sake of accuracy isn't. Manual modes are provided for a purpose. They allow operator choices which they should. You don't have to use them, but they are still there. I for one prefer to take advantage of a supplied option.
Setup conditions (easy to duplicate):
1.
Place the RBW, VBW & Sweep settings all in manual mode. Set the two bandwidths to a middle setting. Settings for the attenuator or units shouldn't matter. No signal is required.
2.
Change the Sweep to the fastest setting (usually 24ms)
3.
Set the frequency range to whatever you want, the full bandwidth is fine though I never have a need for that. My ranges are usually between 50 & 500 Mhz.
4.
Go to the BW page and start changing either of the two adjustments paying attention to the sweep speed. You can use either the 'jog' dial or the up/down buttons.
You will see it drop to the next slower speed. 5. Now, here where it gets more interesting,
return to the previous setting. Note the sweep speed still slowing instead of returning to where it was. Everytime you make any adjustment to either the RBW or the VBW in either direction the sweep slows down to the next fixed setting forcing one to return to the sweep page and crank to back to the fastest setting allowed. Trying to get a respectable display is a real chore jumping back and forth between BW & Sweep.
This brings up a few questions;
A. Why is it changing in the first place since all settings are in or supposed to be in manual mode??
B. Why are these preset sweep speeds fixed at these 'odd' figures? Some mathematical formula and/or a limitation of the system??
With further testing I did find a couple of exceptions where the speed reversed direction, but only to a certain extent.
And no one noticed this at all?? I trust this was spelled out enough to get a handle on it. If it wasn't please ask where I lost anyone.