[time-nuts] Differences / Jitter Between Frequency Standard Sources

Frederick Bray fwbray at mminternet.com
Thu Nov 24 12:55:34 EST 2011


I have what would probably be considered to be a "newbie" question, so 
please excuse my likely ignorance.

I have a HP 5385A frequency counter, which I am using with an external 
standard.  If I try to compare one 10 MHz standard against another, 
using one as the external standard and the other as the device being 
measured, the readout fluctuates between 10.0000000 and 9.9999999.  This 
happens when I am comparing a Z3801A and the Trimble look-a-like using 
the same GPS antenna and identical cables (including length) between the 
GPS antenna splitter and the two units.  I have also used identical 
cables between the 10 MHz outputs and the counters.   Hence, cable 
variations shouldn't be the issue.

The same thing happens comparing the Timesource 2700 against either of 
the GPS standards.

Is this attributable to the different standards or the frequency 
counter?  I haven't yet set up a dual trace scope to compare the various 
sources directly, but that will be my next step.

Thanks for any comments, etc.

Fred Bray
W6WAW




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