EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: mixtwitch on September 27, 2017, 11:18:54 pm
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Hi Guys,
I've recently bought a Siglent SSA3032X Spec An and am getting used to the interface. Up until now I have been using an old Agilent 8591E.
I'm measuring pulsed 26ms GMSK transmissions of ~25kHz BW at ~160MHz so I'm using the external trigger to capture the pulse. In the past I've set up my Agilent Spec An as shown in the attached pic (VBW, RBW = 1kHz, Sweep Time = 20ms, Span = 50kHz) and this has allowed me to accurately capture and measure the pulse and it's sidebands / envelope.
On the Siglent Analyser, when I set my Span to 50kHz and my BWs to 1kHz, it won't let me choose a sweep time lower than 2s - this is obviously no good as my pulse never gets captured. Funnily if I change the mode from 'Sweep' to 'Auto', it automatically sets the sweep time to 9.694ms (!) and I can intermittently capture some of my signal but because it's in Auto now, I can't tune the sweep time to get the correct timing of ~20ms. Has anyone experienced this before? I'm not sure why I can't go down to 10-20ms in normal manual sweep mode - the old Agilent had no problem doing this, and if it can do it in Auto, suggests that it should be possible to do it in manual sweep mode also?
Anybody's thoughts or feedback would be much appreciated.
Many Thanks,
Dave
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Hi Dave
I plan to call in on you tomorrow.
BTW welcome to the forum.
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Dave, at that sweep speed you are blasting thru the filters and as you can see, the HP allows this but it is also an uncalibrated measurement. The Siglent is being overly protective, though this might also be considered a good thing. When you go into AUTO mode, I believe the analyzer (in this case) no longer sweeps but does a FFT capture which might be of little value to your pulsed measurement. Perhaps you can craft a triggering scheme and get around the restrictions.
W7NGA dan
Seaside, Oregon
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I have notice this too in other scenarios. Not sure why you can't adjust to a slower time. There is another way you can tweak the sweep time somewhat. With sweep set to auto ( will put you in FFT mode ) play with RBW vs VBW. With RBW set to 1KHz as you want, I set VBW to 300Hz which upped the sweep time to near 18mS. Not 20mS as you are shooting for but maybe close enough to see what you are looking for.
I also notice that when you are in FFT mode ( below RBW 30KHz ) you cannot adjust the sweep at all. There are limitations to our inexpensive SAs.
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I sometimes wish that instrumentation included a hidden mode called 'I know what I am doing, and even though what I am requesting makes no sense, please let me do it anyway at my own peril'. :)
W7NGA
Seaside, Oregon