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

Robin Kimberley robkimberley at btinternet.com
Thu Nov 24 13:01:39 EST 2011

Any frequency counter will have an given accuracy  +/- the LSD (least
significant digit), so alternating between  10.0000000 and 9.9999999 looks
perfectly normal to me.

Rob Kimberley

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Frederick Bray
Sent: 24 November 2011 17:56
To: time-nuts at febo.com
Subject: [time-nuts] Differences / Jitter Between Frequency Standard Sources

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

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