Do attenuators around the mixer improve the performance of the tinySA
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There has been some debate on having attenuators around the mixer, it is even suggested it may reduce spurs.
So I did test. First picture is a scan of the 15MHz power calibration signal with 6dB attenuators between LO and mixer and mixer and BPF Second picture without any attenuator Signal improved with a bit more then 6dB and noise a bit less so the attenuators are NOT improving the noise level. The spurs reduced both in absolute level and even more compared to the 15MHz signal (keep in mind the levels indicated are relative to the strongest peak, in this case 15MHz) My guess is the spurs I'm seeing are caused by harmonics of the power calibration signal directly getting into the signal path after the mixer. -- HBTE Files section:?/g/HBTE/files Erik, PD0EK |