VCO settings


I have tested LimeSDR for signal generation. I’m measuring TX signal at 866MHz with the spectrum analyser. I can see some peaks +/-205kHz from the carrier. The level is 50dB below the carrier.

I believe peaks might be caused by VCO. I was able to get rid of peaks by adjusting CSW_VCO manually from 115 to 125. Then I don’t see peaks anymore.

I was able to find this with trial and error. What is causing these +/- 205kHz peaks and what would be the best way to get rid of them?