Using readback signals to estimate radial location on a rotating storage device

Approaches for estimating the operating radius of a head in a hard-disk drive. These approaches may be used in a constant or approximately constant density servo scheme. Statistics, which describe the proportion of high frequency values to low frequency values in a readback signal read by the read/write head of a persistent storage medium, such as a hard-disk drive (HDD), are maintained. An estimated location for the read/write head using the statistics is determined. The estimated location may be expressed as an estimated operating radius, which is an estimated distance from the center of the magnetic-recording medium to a current position of the read/write head. Based on the estimated location of the read/write head, an estimated clock frequency for a readback channel to use in reading the servo data stored on the magnetic recording medium is determined. The readback channel reads the servo data using the estimated clock frequency.