Comparison of distant Cs-clock monitoring methods

National Standards laboratory, VTT/AUT in Finland derives it time from four Cs-clocks: three Oscilloquarz 3210 and a HP 5071A. Oscilloquarz clocks are situated in a special access controlled subterranean facility. Clock phases are compared to HP 5071A and GPS-time using three different simultaneous remote measurement techniques. The methods are TV-frame sync. pulse measurement, GPS-second tick comparison and optical 2048 kHz synch. signal comparison. Thus annual delay variations and drift of remote measurement systems can be estimated. Short term stability is about the same for all those methods (30 ns), optical connection is the best. Long term stability is around 100 ns/year. All the methods suffers from phase jumps the origin of which is not clear in all cases.