Abstract: Position error values are obtained from a transducer head while following a plurality of servo tracks with a servo loop that band-blocks a frequency range that includes F, a nominal rotation frequency. An estimated difference distribution is derived from the position error values, the difference distribution having a first frequency component at a positive frequency ?2*F. A scalar track squeeze magnitude indicator is derived from the estimated difference distribution so that the indicator to be transmitted depends on the frequency component.

Abstract: Position error values are obtained from a transducer head while following a plurality of servo tracks with a servo loop that band-blocks a frequency range that includes F, a nominal rotation frequency. An estimated difference distribution is derived from the position error values, the difference distribution having a first frequency component at a positive frequency ≦2*F. A scalar track squeeze magnitude indicator is derived from the estimated difference distribution so that the indicator to be transmitted depends on the frequency component.

Abstract: Disclosed are methods and systems for more accurately measuring the performance of a data-storage device by compensating for the repeatable runout (RRO) errors that are written-in to tracks during manufacture. During the manufacturing process, the disc is divided into zones containing a number of tracks. A representative RRO, known as the coherent RRO (CRRO), in each zone is obtained by sampling the position error signal (PES) of some or all of the tracks in each zone and, in one embodiment, using the average PES for the zone as the CRRO. The CRRO, which is the majority of the PES, is removed from the PES to create a corrected error signal (CES). The CES is used to evaluate the performance of the data-storage device rather than the PES. Because the CRRO does not affect the performance of the data-storage device, removing it results in a more accurate measurement.