The present invention is directed to a method and apparatus for improving
spiral-based position correction system stability via kernel frequency
component modification. In one embodiment, a disk drive includes a disk
surface with servo information written thereon, wherein the servo
information includes repeatable runout. The disk drive includes a servo
system having an error transfer function. Frequencies, where the error
transfer function may experience phase changes, are determined and the
direction of such phase changes are also determined. A kernel, which is
used to calculate position correction values to compensate for repeatable
runout, is provided. Phases of frequency components in the kernel, which
correspond to the frequencies where the error transfer function may
experience phase changes, are rotated.