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Measurements of a signal's spectral content using narrow-band filters and heterodyne techniques are still widely used for component testing for magnetic recording. Most of these measurements use simple square-wave patterns. In contrast, maximal-length pseudo-random bit sequences (PRBS) are in many ways ideal patterns for characterizing magnetic recording channels. Almost all the important characteristics of a recording channel can be obtained from measurements of the PRBS spectrum and the associated noise spectrum, without reference to the actual readback waveforms. These include estimates of the signal amplitude, resolution, nonlinear distortion, transition noise, signal-to-noise ratio, and error rates.