[time-nuts] Methods for comparing oscillators

Ed Palmer ed_palmer at sasktel.net
Mon Aug 3 16:45:20 UTC 2009


The biggest difference between the 5370 and the 5372 is the single-shot 
resolution.  The 5370 has a resolution of 20 ps while the 5372 is 
limited to 150 ps.  When measuring Allen Deviation, this difference 
means that for a Tau of 1 second, the 5370 can measure down to approx. 
2e-11 while the 5372 can only reach 1.5e-10.  Note that since many 
high-quality OCXOs are spec'ed lower than these numbers, neither counter 
can directly measure them and need help e.g. DMTD or some other 
heterodyne technique.

Ed

Steve Rooke wrote:
> 2009/7/31 John Green <wpxs472 at gmail.com>:
>   
>> 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
>>     
>
> What's the difference between a HP 5370A and a HP 5372A for this type
> of measurement?
>
> 73,
> Steve
>
>   
>> 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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>>     
>
>
>
>   




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