Most of this discussion of comparing clocks has been about time interval. The Racal 1992 has a function called "Phase A rel B" that reads the phase angle in degrees regardless of frequency.
At one time I had two HP Z3801 receivers and three 1992 counters, so it was natural to compare the two receivers with phase. There is no concern about the minimum interval between A and B. It does not matter which comes first. There is no sign with the 0-359 measurement. So what you do is record the phase angle reading with time (manually in my case, but there is a connector for GPIB). The rate of change gives the error, where one count is 1/36th of a nanosecond for 10 MHz oscillators. Cable length matters if you want the absolute difference, but a relatively steady phase (it isn't noiseless) over an adequate amount of time yields satisfactory results for adjusting rubidium and cesium oscillators. You don't need a precision external reference when you are dealing with one part in 360. The noise is about 5 parts in 360. Comparing instantaneous clock display times is another matter altogether. Bill Hawkins Age disclaimer: My memory isn't what it used to be. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.