[time-nuts] Methods for comparing oscillators
Richard (Rick) Karlquist
richard at karlquist.com
Thu Jul 30 16:38:11 UTC 2009
You really need to mix down to a low frequency beat note as in the
HP5390 system. There is a huge increase in sensitivity by doing
that. It is not difficult to make a mixer circuit.
Rick Karlquist N6RK
John Green wrote:
> 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.
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