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A phase-comparison experiment using a two-way communication link at 14.2/11.5 GHz via a geostationary satellite and a single groundstation is described. Links of this kind can be used in applications where a high degree of phase synchronization is required between signals at frequencies of the order of gigahertz, which are derived from remotely located high-stability clocks, or where a high degree of fractional-frequency stability between remote clocks needs to be maintained. The link precision was found to be better than 10 ps over intervals in the range 10-1000 s. At these and longer timescales, the link is more stable than a rubidium standard. Present fractional-frequency stability capabilities are better than 10-14 in 1000 s and indicate better than 10-15 in 24 h. Improvements may lead to 10-15 in 1000 s and a few parts in 10-16 in 24 h. In the latter case, the link performance would exceed the capabilities of present H-maser in the region between a few times 103 and 104 s. Preliminary estimates of the link performance for a multistation setup indicate that ionospheric variations may determine the overall fractional-frequency stability.