On 2/20/16 10:22 AM, Attila Kinali wrote:
Moin,
Looking at the phase data, you can see that jitter of the pulses
of two nodes is <+/-170ps, with the average being pretty much in a window
that is samler than +/-70ps.
For the other *DEV plots, I also added measruements of the Teensy 3.1
oscillator stabilty that I got from Jim Lux a while ago. There are
two traces, one is the raw data and another one with the temperature
dependence removed using a linear fit. As the oscillator we used is
an Abracon ASVTX-09, I expect our stability to be better, but not
a too big difference (at most an order of magnitude at 1s).
I don't know that the crystal and oscillator on the Teensy is all that
wonderful. Your Abracon is an integrated unit, so I would expect it to
be substantially better.
Don't forget that the teensy measurements were made by latching the 16
MHz clock in the ARM core when the 1pps from the Rb arrived. So there's
all the issues with threshold noise/risetime wrapped in there. There was
no attempt to have terminations or anything (although the coax from the
Rb to the teensys was about a meter long). The teensys are powered off
the USB.
I was more interested in "teensy:teensy" matching (and of course, it's
fun to just measure stuff).
Also, extrapolating the Teensy oscillator ADEV back to 0.1, it seems
like the clock sync generates a synchronity that is two orders of
magnitude better than what the cheap crystals of the Teensy do.
I would expect the ASVTX-09 to be better (it's a TCVXO after with
a phase noise spec of <-135dBc@1kHz and a temp dependence <2.5ppm over
operating range) and also the clock sync to have an effect. But getting
two orders of magnitude improvement seems to be too much. Hence I am
not sure whether the measurement setup we had is flawed and gives
us better numbers than we actually achieve.
I wouldn't be surprised by this at all. The teensys were run in a very
non-ideal environment, so their performance is probably substantially
worse than the crystal that's on the board.
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
