So first post here. I am still new to VA, so bare with my likely poorly explained questions. Using 2130's and MHM 5.51 at work, to carry out work on a coal plant. I confidently collect and analyse, but looking here to broaden my knowledge. One question I thought to start with, was with early stage bearing faults. I have noticed now and then whilst analysing given pulleys with early stage faults in Peakvue. The levels will be very low and have not become noticeable as a peak and harmonics on the Velocity spectrum. Yet they may appear as sidebands on an excitation frequency in the velocity spectrum. Could anyone please explain this to me??