An apparatus, method, and system for providing a fine adjustment for
transducing head positioning in a hard disk drive (HDD). The apparatus,
method, and system include reading a positioning error field wherein the
resulting signal is a substantially sinusoidal position error signal
(PES), filtering the PES to remove low frequencies and attenuate high
frequencies, sample the filtered PES at a multiple of the channel
frequency, filter the higher frequency harmonics, down sample the PES,
and provide a signal proportional to the amplitude of the down sampled
PES. This signal is the reference signal to the head positioning servo.