[time-nuts] My TICC came in the mail yesterday

Andrew Rodland andrew at cleverdomain.org
Fri Feb 24 12:59:50 EST 2017

Which means, after a bit of scrounging for some BNC to SMA adapters, I
have some plots worth using (more or less) of my clock!

Background info: my clock's main purpose is to be a GPS-disciplined
NTP server on an Arduino Due clone board. As such, accuracy beyond
tens to hundreds of microseconds isn't really relevant. But for purely
time-nut reasons, it has an Rb oscillator (cheap surplus X72), and for
similar reasons it has a PPS output generated by the CPU timer. I
didn't hack the Due apart to replace the crystal, so the CPU clock
(84MHz) is asynchronous from the Rb, which has some limitations, but
also introduces a nice little bit of dither

The TICC is set up with 10MHz from a Spectracom NetClock, chA from a
(probably insufficiently thermally stabilized) LTE-Lite, and chB from
my clock. Output is in Timelab mode.

A representative bit of the phase plot: http://i.imgur.com/cRXv9ia.png

You can see all the quantization noise on my clock, but also that in
the ~100s region, it does better than the LTE-Lite. You can also see
the nice smooth (at short time) plot of the LTE-Lite which gives me
some good faith in the TICC.

ADEV plot so far: http://i.imgur.com/DLb15rt.png

Timelab loses the thread a little bit and comes up with negative
computed deviations for my clock for some tau. Not sure how much of
that is due to instrument limitations, and how much is due to the
noise being not-really-independent, since all three clocks are GPS
receivers, with rather nearby antennas. Still, more than I've ever
seen before!


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