  In fast ramping synchrotrons like the Fermilab Booster the conventional
methods of betatron tune evaluation from the turn-by-turn data may not work due
to rapid changes of the tunes (sometimes in a course of a few dozens of turns)
and a high level of noise. We propose a technique based on phasing of signals
from a large number of BPMs which significantly increases the signal to noise
ratio. Implementation of the method in the Fermilab Booster control system is
described and some measurement results are presented.
