Can I enter the sweep time manually in Spectrum Analyzer mode?
Yes you can. You can go into the sweep menu (MT8222A, MS272XB) or "MEAS/DISP" menu (MS2711D, S332D, S312D, MT8212B) and select "Min Sweep Time" and enter the desired sweep time. If you enter a time that is faster than what the instrument is capable of then the instrument will change the sweep speed and default to whatever the instrument can do. For every measurement point, the instrument spends a certain time and if it is too fast, then it is measured again. This is why the actual sweep time is usually a little bit longer than the requested time. In zero span mode, the sweep times are exact.