Hello to the group, Thanks for interesting discussion. I found a nice plot in"Measurement, Instrumentation, and Sensors Handbook, Second Edition", ( John G. Webster,Halit Eren), at 42-24 page. It shows that in short term stability (tau 1 - 10 s) dual mixer method is most sensible, in long term stability TIE and DM results are similar. I'm going to do the same mesurements with Rb standard (Pendulum 6689) as DUT. Data is now collecting. SD