The Swiss-based METAS Time & Frequency metrology laboratory acquired a T4Science hydrogen maser in 2002. The maser was commissioned at the beginning of 2003. In June 2003, the maser started to contribute to the generation of the UTC (CH) and TA (CH) time scales. The Swiss time scales are currently generated from 3 cesium clocks and 1 hydrogen maser. The clock results are sent monthly to BIPM for contribution to the generation of TAI and UTC. The hydrogen maser is also used in combination with a DDS synthesizer to generate UTC (CH.R), a real-time realization of UTC (CH). The daily steering of the UTC (CH.R) is based on a prediction of the hydrogen maser time scale over 1.5 d. Although the hydrogen maser doesn’t have an Automatic Cavity Tuning (ACT) system, we have found that, despite the frequency drift, the time scale is extremely predictable.
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