I have a suggestion to Siglent, if they listen here. I have an SDS1104X-E and an SDG2042. They work well together to do Bode plots. The process is very slow however. The function is great for making measurements but useless for tuning a radio IF, for example, in real time. It is fairly easy to make real time swept measurements with the pair by having the generator sweep at the desired rate and setting the scope sweep time to match. You can even have the second channel generate a sync pulse. There is a sync output on the back of the generator that works fine too. The front panel connector for channel 2 is just more convenient to use!
The display you see on the scope is the envelop of the test signal as it is swept through the pass band of whatever it is that you are testing/tuning. It is perfectly useable as it is. It would that much nicer, however, if you could set the vertical display of the scope to give you the log of the output voltage, a dB scale in other words. I realize that there are mathematical issues with doing this on a signal that passes through zero but there are reasonable things you could do about that. Just setting a minimum displayed level for the current sensitivity setting for example.
Of course you can do much the same thing with an external log amp and I have one on order. It just seems to me that the scope firmware could do this sort of thing and make the external amp unnecessary....
Perhaps you have found it works some amount faster if you turn ALC off. (Channel Gain Auto/Hold, select Hold) But in this case you need manually first check what is maximum level and manually set channel V/Div so that signal do not clip.
Naturally maximum dynamic range is now limited and not anymore up to even 140dB.
Still it is quite slow. I have not now available SDS1000X-E for check, I am far away from my homeland.
But I just tested using SDS2000XPlus and one case, simple 3 xtal 11MHz ladder, 20kHz span swept with 250Hz steps. ALC off, 17s and ALC On 51s. SDS2000XPlus also slows speed down when ALC On and signal out from DUT is very weak, near noise.
Attached this test image when measured 17.1s sweep repeat interval. And yes it is still slow. But not hopeless slow even for fine tuning filter. For rough preliminary adjust no need even this freq resolution.
Depending case and what we are adjusting, rough steps do not need high freq resolution so it can speed up and then use higher resolution when do some fine adjustments. Here was used 250Hz resolution. Maximal with 20kHz span is 40Hz.
Naturally analog sweeper and analog scope can be much faster, but even then, if filter is enough narrow, there need reduce speed. In history I have used analog scope and sweeper quite lot, but in history also special instruments like example ancient R&S SWOB.
Just same reason why sweeping spectrum analyzer slows down sweep when RBW is more narrow. Now our "RBW" is this filter under test. Some usual IF filters are of course so wide and not extremely steep, it is not reason for this slow speed in scope BodePlot. But, it need also remember that DUT is unknown and PB need handle it even if there is very steep edge.
Now when BodePlot sweep, it can not know what is next step, it can be just up to full dynamic range step. It need keep speed so slow that even this is possible. Because DUT is unknown. It can not predict DUT response and adjust optimal speed. it need use worst case speed and then of course time what need command SDG and wait it settle and give also time to DUT for settle. And if ALC is On, then adjust optimal input channel V/div. And after all ready then start measurement. Plot data to primary table and after then go to next step. Bode plot display is secondary, it only draw to display what data is in primary full resolution table.
Lets hope some day it is possible that also user can adjust this bode plot step delay and also turn it to wide mode. (as we know it listen only this frequency what it have asked from SDG, it works like frequency selective level receiver... in some cases, when DUT do freq conversion (simplest example, mixer), we need full span wide level "receiver" *if we can not adjust offset, (if offset is known and constant.))
SDS2kX+ is not same as 1kX-E but also there is difference in speed when ALC on/off
20kHz span, 250Hz freq steps. ALC Off aka Input Channel Gain:Manual 17s sweep interval
(Image)20kHz span, 250Hz freq steps. ALC On aka Input Channel Gain: Auto 51s sweep interval (no separate image, only bottom right corner have less noise.)