A synchronous sampling data detection channel includes a data transducer head positioned by a servo-controlled actuator over a recording track of a rotating data storage disk, a preamplifier for receiving electrical analog signals magnetically induced by the data transducer head from flux transitions present in at least the servo information field, a digital sampler for synchronously sampling the electrical analog signals to produce digital samples, and a Viterbi detector coupled to receive digital samples from the synchronous sampling data detection channel for decoding 1/4 T coded wide biphase servo information patterns patterns as maximum likelihood servo data sequences, wherein the wide biphase magnet patterns are arranged e.g. as ++-- magnet patterns for a binary zero information value and --++ magnet patterns for a binary one information value.