[time-nuts] Divider pecking order ?

John Ackermann N8UR jra at febo.com
Mon Mar 22 02:20:01 UTC 2010


I'd love to see the results of some well designed and controlled jitter 
measurements.  I did a bunch on the TADD-2 and a single-channel 
prototype, but they weren't as rigorous as this group deserves.  (The 
short version is that the tests pretty consistently show jitter standard 
deviation of less than 20ps or so, but how much of that is 
instrumentation versus the divider itself is unknown.)

One suggestion is to check the tempco as the folklore is that the 
cascaded-chip designs can have significant drift over temperature.

Finally, if the hardware is available, a suggestion for the methodology 
is to use a pair of same-design dividers fed from a common 5 MHz or 10 
MHz source, but with unequal coax length to introduce a few nanoseconds 
delay between them.  Then use one on the start channel, the other on the 
stop, and divide the results by sqrt(2).

John



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