Why does the LimeSDR USB Rx have so many spur?

[Dynamix_yang]

Hi,
I load the default setting in LimeSuite GUI and try to receive a single tone from a SMU200A RF Gen. I use default settings and tune the default clk rate and 1200MHz Rx freq. I input a -10dBm 1200.4MHz single tone signal and use the min gain by changing the lna gain and pga gain to min. I get the waveform from fft viewer but found many spurs. How do these spurs come form? I tried to cal the rx channel but things didn’t become better.

Thanks!

[N0YKG]

A directly connected -10dBm signal may still be a bit hot. If you lower your input 3 dB, do the spurs go down 3dB, 6dB, or 9dB? That will tell you if these are real spurs on your signal, or are compression/3rd order effects.