Greetings Erik,
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? ? ? ? ?IMHO the Si5351 spectral purity screen capture is a good example that illustrates the great value of the tinySA instrumentation concept for checking out the quality of a signal source.?
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The comb of sideband spurs shown here caught my attention as I couldn't remember seeing anything similar on some Si5351 spectral purity tests I did in the past. Attached is a screen capture of the output from one port of a prototype wired Si5351 that I once did spectral purity measurements on. At the time I had an Si5351 module prototype wired to an ESP8066 development board that was remotely controlled via WiFi. Although I found that there were a few randomly spaced spurs which were about 60dB below the 57.x MHz carrier and poking up above the -80dB noise floor as shown in the attached screen capture I didn't see a comb of spurs as shown in the tinySA Si5351 spectral purity photo.?
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It appears that the tinySA may have revealed that there was some digital noise getting into the Si5351 generator circuit, possibly riding the power rails.
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Best Regards,
Tom, VA7TA
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