[time-nuts] another Ebay mixup, 5370
SAIDJACK at aol.com
SAIDJACK at aol.com
Sat Jun 9 16:16:55 EDT 2007
In a message dated 6/9/2007 08:26:06 Pacific Daylight Time,
tvb at LeapSecond.com writes:
>Many of us have 5370; can you describe exactly the setup
>you're using so we can make apples-apples comparisons.
>What source, what cable, what connectors, switch settings,
>int/ext ref, etc.
this was the recommended setup (by HP) for checking the internal noise. Feed
the 10MHz output back to the input using a short cable, and set the unit for
"COMMON" input, setting 50 Ohm impedance etc.
In the meantime I did some more tests, and found the following:
1) The sine-wave output is crappy. The sine wave has some sort of
"Class-B" cross-over distortion, and it measures a whooping 200ps RMS jitter on my
Wavecrest jitter analyzer (>400ps pk-pk). Compare that to 2.7ps RMS jitter I
measure on our Fury 10MHz output. Definitely the crystal got damaged, or
The unit has about 2x better jitter performance (around 50ps RMS) if I feed
a clean Fury 10MHz into it. I think the 10811 OCXO or the internal driver
circuit may have gotten damaged.
2) As described earlier, with the Fury GPSDO driving the unit's ref
input, and very careful adjustment of the trigger level I can get RMS readings
<30ps with good time-intervall output. This is on a setup as follows:
REF-IN driven by Fury unit A 10 MHz output
One input driven by second Fury unit B 10MHz output
Second input driven by PRS10 GPSDO 10MHz output
Unit set to measure +-Time Intervall
I am happy with that result, except the trigger pot sensitivity, it's very
hard to set correctly, and sometimes jumps to >60ps RMS by itself. I hope to
be able to replace the 10811 - although feeding it externally is not a bad
idea, and hopefully get the full <30ps performance in "preset" mode after full
Has anyone had similar problems?
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