[time-nuts] Methods for comparing oscillators

[John Green]

I've been hanging around and reading long enough to understand that when
measuring the differences between oscillators the preferred methods are the
HP 5370A Time difference counter or the dual mixer method. I want to
evaluate some ocxo's and Rb sources against either a Tbolt or Z3801 and I
don't have either method available. What I have used in the past is an HP
Infinium scope with the reference fed to one channel which also provides
sync and the DUT to the other. I have tested 2 ocxos that were so close that
the two waveforms did not move by a detectable amount in a 30 minute period.
I realize that this method will require very long observation times when
looking at more stable sources. I am not looking to get absolute data, just
comparative. Given what I have to work with, is there a better way? I use an
Agilent 89441A Vector Signal Analyzer for signal quality measurements. I can
see 60 Hz sidebands at least 60 or 70 db down and while I can't measure
phase noise, I can  tell a clean oscillator from a dirty one. For instance,
there is a world of difference between the signal generated by an HP8920 and
a E4430B.