Anomalies in Determinations of Time Scale Uniformity Based on TV and Loran C Comparisons

Abstract

The method of generating the NRC atomic time scales UTC(NRC) and AT(NRC) is outlined, and estimates of their uniformity are derived from intercomparisons of the NRC primary standard, Cs III, and the group of atomic clocks maintained at NRC. Comparisons between UTC(NRC) and other national scales through reception of television and Loran C signals are outlined, and it is shown that conflicting results arise from these two methods. In addition, the uniformity of UTC(NRC) deduced from these comparisons appears to be significantly worse than that determined from internal clock comparisons. Variation in signal propagation delay for both TV and Loran C transmissions is proposed as a possible explanation both for the disagreement between TV and Loran C time scale comparisons and for the apparent degradation in the uniformity of UTC(NRC).