Back to topic, comparison...
FFT of SDG1062X and 2122X, sinewave 1khz, appx 0dBm @50Ohm:
SDG2122X:
SDG1062X:
I’m new to the forum, however I watch it since ~2019.
In my opinion many people don’t try to understand FFT backgrounds and they do misinterpreting the results. Somebody should create new topic like “FFT good practices / primer”, independent of the equipment vendor. FFT can be confusing… FFT windows may sound confusing, almost each vendor has own interpretation of FFT, etc… But all are base on the same math formulas.
For beginners:
- Check your DSO ADC bits, and if:
- it’s 8 bit, ignore everything below 48dB in respect to dbV should be ignored.
- it’s 10 bit, ignore everything below 60dB in respect to dbV should be ignored.
- it’s 12 bit, ignore everything below 72dB in respect to dbV should be ignored.
- it’s 14 bit, ignore everything below 84dB in respect to dbV should be ignored.
- it’s 16 bit, ignore everything below 96dB in respect to dbV should be ignored.
… and so on.
- Use the vernier and adjust that your wave to covers 90 - 95% of the p-2-p signal on the screen.
- Don’t use any kind of averaging, ERES, highres, etc.
- Use AC coupling (most scopes will be fine with frequencies > 30Hz in AC coupling, check yours).
- Use plenty of samples… it will depend on your scope.
- Ignore myths...
As good start I suggest to check THD + Scope published by W2AEW about 3 years ago:
If anybody is in high-end audio, you should ignore oscilloscope and use good quality ADC/DAC combined with software like Audio Rightmark, ARTA, or REW suite. ...Or buy specialized equipment, however it may come pricey…