FFT: low magnitude peaks centered exactly 1 Hz apart across whole spectrum I am running an fft on 60 seconds of data sampled at 1289Hz. The fft is run every second on a single channels fifo buffer which is also updated every second. The algorithm used is numpy rfft with a numpy blackman window. The fft output is normalized to the max fft value. This is all on a raspberry pi 4 with custom adc board that uses an AD4114. Am sampling 8 channels (16 in differential mode) as fast as the AD4114 can go which works out to 10.312kHz.
The following screen shots are with a 20Hz sign wave applied to one of the channels.  Similar low magnitude peaks appear with real data a transducer attached to the input. There are low magnitude peaks centered exactly 1Hz apart right on top of each whole number. Is this normal? Like a normal artifact of the fft? Possibly something wrong with my data? I am a casual fft user and am hoping someone may have some advice for me. Thank you very much : )
Is this normal?

No

Like a normal artifact of the fft?

No

Possibly something wrong with my data?

Yes. Could be a data problem, could be a hardware problem, could be a SW problem, could be real. You seem to have a very large DC offset in your data. Without knowing what exactly your data, is I can't tell whether that's expected or if it's a problem.