  A system was developed for bunch-by-bunch detection of transverse proton and
antiproton coherent oscillations based on the signal from a single
beam-position monitor (BPM) located in a region of the ring with large
amplitude functions. The signal is digitized over a large number of turns and
Fourier-analyzed offline with a dedicated algorithm. To enhance the signal, the
beam is excited with band-limited noise for about one second, and this was
shown not to significantly affect the circulating beams even at high
luminosity. The system is used to measure betatron tunes of individual bunches
and to study beam- beam effects. In particular, it is one of the main
diagnostic tools in an ongoing study of nonlinear beam-beam compensation
studies with Gaussian electron lenses. We present the design and operation of
this tool, together with results obtained with proton and antiproton bunches.
