Real-time microprocessor monitoring of skew angle in a compact cassette multitrack magnetic tape system

Tape-skew variation imposes one of the limits on the upper recording frequency at which digital data may be read coherently from a multitrack tape. It can be measured using timers controlled from marker transitions on the outer tracks of the tape. The timers are interfaced to a microprocessor which applies a ratio technique to indicate a bit-cell displacement which is insensitive to tape velocity and circuit variations. Spectral analysis of the skew of C60 compact cassette tapes reveals a cyclic variation of skew angle of about 2 Hz with a total displacement across the tape of within one bit-cell at 10kb/s. The skew angle is not always uniformly distributed across the tape due to tape deformation. The computed values of average tape deformation are 0-67 ¿m, 0.85 ¿m and 1.08 ¿m for C60, C90 and C120 tapes respectively.