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Two-way satellite time and frequency transfer (TWSTFT) has become an important component in the international network for comparing time scales. To employ the full potential of the technique a calibration of the internal delay of each ground station is necessary. Only a few calibration campaigns have previously been carried out in the European network of TWSTFT links. We report on the first recalibration of TWSTFT links during a campaign involving six European time institutes. The campaign was performed using a portable ground station assembled and operated by TUG/Joanneum Research, Graz, that visited the sites of INRIM, NPL, OP, PTB, SP, and VSL, travelling a total distance over 7000 km during a three-week period in October/November 2005. Differential delays of earth stations were determined in the common clock mode relative to the portable station. Combined uncertainties ranging from 0.9 ns to 1.3 …