A data recording medium, such as a magnetic recording hard disk, has data tracks
with pseudo-random binary sequences for the servo information used to control the
position of the recording head in the disk drive. A first pseudo-random binary
sequence (PRBS) and a second PRBS identical to the first PRBS but shifted by a
portion of the period of the first PRBS are located between the track boundaries
in alternating tracks in a first region of the servo pattern and between the track
centers in alternating tracks in a second region spaced along the track from said
first region. A servo decoder in the disk drive has two correlators, one for each
PRBS. Each correlator outputs a dipulse when its PRBS repeats. The difference in
amplitude of the dipulses represents the head position signal. The dipulses also
control the amplifier for the signal read back by the head and the timing of the
track identification (TID) detector.