| 摘要 |
PURPOSE:To detect a magnetic recording medium easily causing a peak shift by reading a signal written at the highest write frequency and measuring a difference between an output level of the signal center frequency to be reproduced and the output level of the frequencies in the vicinity of the center frequency. CONSTITUTION:A signal written on an inner circumferential track 11 of a magnetic recording medium 1 at the highest write frequency is read from a magnetic head 2. The signal read by the magnetic head 2 is amplified by an amplifier circuit 3 and its output level is measured by a spectrum analyzer 4 and the output level of the center frequency of the signal written at the highest write frequency and the output level of an optional frequency near the center frequency of the signal are obtained and when the difference is a prescribed value or over, the medium is discriminated to be a non-defective medium. Since it is possible to detect the spectrum waveform of the read signal having a wide range, the magnetic recording medium causing easily a peak shift is detected.
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