TIME AND FREQUENCY COMPARISONS BETWEEN FOUR EUROPEAN TIMING INSTITUTES AND NIST USING MULTIPLE TECHNIQUES

Bundesanstalt (PTB) performed an intense comparison campaign of selected frequency references maintained in their laboratories during about 25 days in October/November 2004. The active hydrogen maser reference standards used at all laboratories served at the same time as frequency references for the institutes ’ fountain frequency standards. The fountains of IEN, NPL, and OP were operated for most of the time during the same period, and results of the fountain comparisons are given in an accompanying paper. Three techniques of frequency (and time) comparisons were employed. Going beyond the standard procedures, two-way satellite time and frequency transfer was performed in an intensified measurement schedule of 12 equally space