[time-nuts] 5370B problem

SAIDJACK at aol.com SAIDJACK at aol.com
Sat Jun 23 05:18:58 EDT 2007

Hi guys,
has anyone seen phase jumps of the  "nanoseconds" range without any affect to 
the picosecond display in  the 5370B before?
This problem has been appearing before I ever opened the unit, so it's not  
related to my calibration/mods.
What is happening is really weird:
Whenever the unit reacheas about 13.5ns TI A-to-B input difference (in +-TI  
mode), the output measurement jumps around in complete nanosecond  changes.
The picosecond range display is not affected by this!!
The unit is in 100-samples averaging mode, set up to "TALK" mode on the  GPIB.
The attachement is a zoomed-in version of the longer-term measurement sent  
out in the previous email. Scale is about 12.8ns to 14.35ns.
The LED Display can be seen to jump around when this happens, but only  the 
nanosecond digits(!) the three picosecond digits remain stable with little  
noise such as:



This seems to me to be a digital problem, maybe in the averaging algorithm?  
Maybe because the unit is in GPIB talk-only mode with the GPIB-to-RS232  
converter attached?
Maybe it's an "anti-coincidence" calibration issue?
In the attached PDF you can see it jump back and forth by about 1 or 2  
nanoseconds. I have seen it jump 5 or more nanoseconds as described  above.
It happens (repeatably) at around 13.5 nanoseconds.
Has anyone seen this as well?
thanks in advance,

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