[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.


Hi Tom,
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 
something else.
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?

************************************** See what's free at http://www.aol.com.

More information about the time-nuts mailing list