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

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Mar 17 21:59:16 UTC 2010


The problem could be due to the effect of synchronisation of the divider 
output to an internal 100MHz clock.
A close look at the circuit would be required to see if indeed this occurs.
A quick glance indicates that the TB out signal appears to be always 
synchronised to an internal clock.

Bruce


John Miles wrote:
>    
>> I would tend to say that the divider is pretty lousy for short
>> term, but it is all fine for longer runs, right?
>>
>> Is this what I should expect from a TTL/ECL divider chain
>> designed in the '70s-'80s? How would this compare to a modern
>> divider chain, like the PIC divider or David Partridge's divider board?
>>      
> The 5370 residual plot I mentioned in the other message was taken under
> similar conditions as you describe, but with a TADD-2 divider, and is almost
> 100x better.  IMHO the 5328A solution doesn't look like a good one, since
> any inexpensive digital divider should be able to beat it.
>
> It's true that factors like trigger levels and attenuator settings matter,
> but this will be observed at the tens-of-picoseconds level in my experience,
> not at 1ns+ timescales.  Triggering on the correct edge is likely to be more
> important.  Try it both ways and see if you notice a difference.
>
>    
>> Since I get a straight line pretty much up to 500s or so, do I
>> conclude that the divider dominates the system noise up to there?
>>      
> That's very safe to say (again, load that residual .tim file and display it
> next to your result and you'll understand instantly).
>
>    
>> Of course, the 5370A timebase drift has to be taken into account
>> but is not subtracted on that plot.
>>      
> Slow drift in the 5370 timebase isn't an issue for two-channel ADEV
> measurements.  If you had a problem involving excessive noise from either
> the timebase or trigger circuits at timescales close to your 1-second tau
> period, it could degrade the results, but that's extremely unlikely.
>
> -- john, KE5FX
>
>
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