On a DC free block modulation code

A rate 8/10 modulation code, which is suitable for a recording channel with a transformer-coupled rotary head, is developed. The code has the following advantages. Because is short, overwrite noise, when it is overwritten, is small and the peak shift of the playback signal is also small. Disturbance of recording current caused by low frequency cut-off characteristics of recording circuit is small since the power spectrum in the low frequency region is low. Because there is a particular code pattern, which appears only at the boundary of two adjacent words, word re-synchronization is possible after it is lost by burst error. The code is evaluated from the point of view of the overwrite noise, influence of the low frequency cut-off of the rotary transformer and side reading crosstalk noise at guardbandless recording of home use VCR. The result shows the code is suitable for this type of rotary head recording channel.