Experimental study of the off-track dependence of medium noise using a mode projection method

An experimental scheme is developed to study medium noise properties at various off-track positions. Amplitude fluctuation and transition jitter are studied by projecting the measured noise onto the two leading noise modes: amplitude fluctuation and position jitter. Comparison with the directly measured waveform shows that these two modes well represent the actual amplitude and position fluctuations and that these two modes dominate the entire noise distribution. The magnitudes corresponding to both modes increase with off-track position. Off-track dependence of the power percentages from the two leading noise modes for dibit transitions is investigated in detail. This dependence is found to be influenced by the noise level of the disk as well as the sequence of the dibit pattern, i.e., Hard-Easy (HE) and Easy-Hard (EH).