Looking closer on the spectrum device after the fix on development branch i think i found some problems with the representation of the sensitivity scale on the y-axis on the device. All the issues can actually be seen at the example on the wiki (https://community.bistudio.com/wiki/Arma_3_Spectrum_Device) itself, so i will take that as an example.
1.) #EM_Values do not fit with the values on the y-axis. #EM_Min is defined with -60 and therefore should be at the bottom (as its also described in the picture), #EM_Max is -10 and therefore should be on the top, however they are not.
The values set via #EM_Values seem to be at the right place, but because the scale seem to be wrong they don't fit. 140.85,-50 (as defined at the bottom of the wiki page), its actually shown at 140.85,-10 in the picture. I tried that out myself with the same #EM_SMin and #EM_SMax values ingame and got the same result.
2.) The steps on the scale seem wrong. Even in the current (probably wrong) state, -50 would be on the top, the range from 50-60 could not been shown on the device.
So it seems the steps that are shown should be -20,-30,-40,-50 and not -10,-20,-30,-40 as it is now (even if the order is in question). This also fits in well with how the signals are currently shown. If the scale would be just reversed, 140.85,-50 would be shown at 140.85,-40.