Tranciever Тюльпан-DSP

[RX9CIM]

Noise floor must be flat in ddc version of tulip, of coarse without antenna. How I understand your problem that you have like noise pulses or spletter?
For search cause of this problem your must to use classical methods- search the path of interference, like connect antenna to ADC with bypass of BPF and LNA.
For me it is unique situation because all hiqsdr that I view do not have this problem.
In my hiqsdrminiV2 have interferences on some frequencys from power inverter, but it view like wide (5-10kHz) single tone tone peak with noise. Interferences not often and outside the range of ham radio bands.