Improved studies of b fragmentation in Z0 decays We present preliminary results of a new measurement of the inclusive b quark fragmentation function in Z0 decays using a novel kinematic B hadron energy reconstruction technique. The measurement is performed using 350,000 hadronic Z0 events recorded in the SLD experiment at SLAC between 1997 and 1998. The small and stable SLC beam spot and the CCD-based vertex detector are used to reconstruct B-decay vertices with high efficiency and purity, and to provide precise measurements of the kinematic quantities used in this technique. We measure the B energy with good efficiency and resolution over the full kinematic range. We compare the scaled energy distribution of weakly decaying B hadrons with the predictions of several models of b quark fragmentation, and also test several hypothesized functional forms. We exclude many of these models and functional forms, and we present a corrected distribution with a small and well defined model dependence. The mean scaled energy is measured with a statistical precision of 0.003 (preliminary).