I opened this new thread as suggested by @dkemxr
after this post Issue with FFT in new Mission Planner 1.3.75 build
I executed FFT to the same file (2021-07-31 17-27-12.bin) in Mission Planner 1.3.74 (on saturday July 31) and then after updating to 1.3.75 (sunday, August 01) I found that the vertical axis amplitudes changed.
Does someone know if there has been any change in vertical axis units in version 1.3.75?
I was trying to adjust a Notch filter for Gyro noise. Taking into account the FFT results for 2021-07-31 17-27-12.bin, I selected
INS_HNTCH_FREQ = 100
NS_HNTCH_BW = 50
INS_HNTCH_REF = 0,142915 (equal to MOT_THST_HOVER)
writed parameters to FC and then I executed another AltHold flight, obtaining 2021-08-01 12-04-17.bin (FFT plots of both files using Mission Planner 1.3.75 can be found in the link to the abovementioned thread).
It seems that there is no substantial difference between the signal after and before filter application. I saw in other threads in the blog plots with significative attenuation of the peaks, so it seems something is not working here. I am a novice with Ardupilot, so perhaps I am not considering something. Comments with suggestions are appreciated.