[time-nuts] HP 5328A Divider / Timebase Output performance

John Miles jmiles at pop.net
Thu Mar 18 01:32:06 UTC 2010


> OK, so I tried this myself. A sloppy setup but never the less... The
> CNT-90 time-base output via a T-connection on B-channel and then over to
> the A input of the HP 5328, selected START A and then the T.B. OUT over
> to CNT-90 channel A. At 100 kHz setting on the HP 5328, the TI A->B
> measurement on CNT-90 shows some jitter, but RMS jitter is below 400 ps
> at least and ADEV readings somewhat below that.

There's one other potential error source in Bert's case that might make his
results look a bit worse than they really are.  TI addresses the 5370 in
talk/listen mode, and I've noticed that it can sometimes get into a state
where the counter appears to skip every other reading.  I've only seen this
happen with 1-pps sources driving both channels but it could conceivably
happen on a 10 MHz test as well.  The result would be 2 seconds' worth of
noise/drift between readings instead of one, which would artificially make
the graph look a bit worse.

So if the counter's display seems to change only after every other START
cycle, that could be happening.  The next test version will allow the
counter to run in talk-only mode with arbitrary measurement periods, which
should avoid this behavior completely.

-- john, KE5FX




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