Hello Volker,
Did you try making the limit more like a box rather than a Spike like I suggested in my earlier response? Since your spike is smaller than 1 RBW the limit test point is being interpolated between the high point and adjacent low points. Unless the frequency bin happens to fall exactly on your high limit line point, it will interpolate somewhere along the steep limit line. This latest version is now drawing what is being tested against so there is no confusion, (the last version improperly drew the limit line as entered rather than the actual interpolated test points)
Ultimately I think this spike in the limit line approach to check for a CW is not ideal with how we implements limit lines and it looks like you had a perfect setup back in 3.1.11 because I can’t even reproduce your original image using the original limit line you provided. I think going towards a box/square shape and being mindful of your RBW will solve this problem long term.
Regards,
Andrew
