Products > Test Equipment
SSA 3021X 500 Hz off calibration
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KE4CDR:
My siglent spectrum analyzer is off calibration, apparently.  From a fresh startup inputing a verified 50.75MHz at 1VPP (checked with my siglent oscilloscope (SDS1102cml) and function generator (SDG1032x) freq is right on) I'm getting a 50.83MHz on my SSA.  Anyone have any ideas why this may be happening and what I can do about it?  Is my setup wrong?  Any help or suggestions as to what to look for would be much appreciated. 
Update:  At span 10KHz the peak is right on 50.75KHz.  If I move the span up to say 20KHz or higher it goes off frequency.  Seems like it shouldn't do this. 
Update#2: Ok this getw weirder and weirder.  So, it seems the 500Hz frequency addition is arbitrarily added and subtracted throughout the span range.  For example at span 50KHz it will flip from 500Khz added to the actual frequency to the correct frequency reading several times going from 50KHz to 51Khz.  There's no specific span difference that seems to initiate the 500khz addition.  It seems random, but repeatable.  The SSA reading of the peak at 50.75KHz goes from the correct freq reading to a reading with 500Hz added throughout the span settings.  It seems just accidental that you set the span on the freq that will allow you to have the correct frequency reading.  Anyone else seeing something like this?  Do I need to call Siglent  for a repair?  I haven't had this thing more than 2 months and I always use a protection circuit on the front end.  Any suggestions? Thanks in advance. 
Kleinstein:
The frequency error depending on the span setting looks a bit like a software problem or maybe a resolution limitation. Especially with a rather wide span the bins may not be fine enough to  have one every 500 Hz. One may have to adjust some settings for a slower scan.

I would not expect this to be broken hardware - more like old firmware or a rather embarissing bug. So a first point would be to check the frimware version and if there is possibly an update.
Broken hardware would be more like off by a certain factor (like 100 ppm) or as the main symptom  too low an amplitude by a lot.
wasedadoc:
I am not familiar with that SA. Does it sweep continuously through the span or only measure at discrete points?
bicycleguy:
on SSA3021xPlus do not get this effect at all
Zenith:
I've just tried this with a Siglent SSA3021X about 2 years old. The 50.75 MHz signal is from a Marconi 2019 sig gen, checked against a Racal 9921 counter, checked against a GPSDO. I'd say it's accurate and stable to within a few Hz. I see nothing like this. I've changed the span from from 10KHz to 20KHz and then all sorts of values. Maybe I've misunderstood this and I'm not doing what you were.

Have you updated to the latest FW?

Is the signal source as accurate and stable as you assume?

I'd be more inclined to trust the frequency reference in the SA than the other two pieces of gear.
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