I think right around 31 Mhz is the actual lower frequency of the lime. Then NCO? or Decimation? take effect to translate it lower, into HF. I “Think” that is the reason for the noise at that frequency is because of this.
I am sure there is a setting somewhere that can negate or null it.
Someone more in the know will chime in to correct my post, surely. U am still learning. I’m a hardware guy & don’t understand a lot of the stuff yet, but getting there.
Ed