[time-nuts] MT3339 PA6H and Racal Dana GPIB

Fabio Eboli fabioeb at quipo.it
Tue Dec 11 23:36:34 UTC 2012

this afternoon the post(wo)man handed
to me the little box with the PA6H
GPS modules. I bought also an antenna
with 5mt cable, so I can use it in the "lab".
The module is up and running, requiring
only  3V3 supply, locking very fast,
about 30s from cold start, here is it, working
with ext antenna:

And now I'm trying to setup a logging session
to try to log interval measurements with the

Now this is what I have done, the goal is to
try to have some jitter measurements for the
PPS output:
- A FE5680A is the timebase for the counter
- the counter is a Racal Dana 1992
- the FE5680A 1Vpp output is connected directly
to rear reference input of the counter
- the counter measures the PPS signal from the
GPS module, Time interval A, 9 digits (single shot)
1nS resolution.

After fighting with the counter's GPIB interface
now I'm logging a stream of time intervals.
I'm not catching all the pulses, but only one each
2 or 3, depends.

- Is this setup enough to get meaningful data?
- If so how long should I log the data?
- If not what should I modify?
- Once collected the data, what kind of analysis
should I do?

And for who have ever used the Racal Dana 1992
with GPIB interface:
I feel dumb, but I could not figure how to poll
the instrument for the availability of last
data. Now the sequence i do is this:
- T1 -> wait for trigger
- T2 -> trigger
- wait 4 seconds
- read result
- T2 -> trigger
- wait 4s etc...

Doing so I catch only part of the pulses, is
there a way to make it better?

This is a graph of the first thousand records:


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