[time-nuts] ADEV query Timelab and TICC

Orin Eman orin.eman at gmail.com
Sun Mar 19 16:16:22 EDT 2017

I've seen similar with my TICC when observing a PPS - can't remember
whether the PPS was from the Thunderbolt or LTE Lite.

There was a distinct glitch on the frequency plot when it happened and it
was pretty easy in timelab to expand the trace around the glitch to take a
better look.

I did not see any such problem when dividing the 10MHz to 1PPS with a
PICDIV so I figured it was due to the GPSDO steering the PPS signal as
satellites appear/disappear - my antenna location is far from optimal.

On Sun, Mar 19, 2017 at 12:57 PM, Tom Van Baak <tvb at leapsecond.com> wrote:

> > I'm probably missing something obvious but don't understand what's
> > happened here so any suggestions would be welcome.
> Hi Nigel,
> Your setup sounds fine. Off-list, send me the TIM files and I'll see what
> happened.
> I know we all love ADEV but in general always look at the phase, phase
> residual, and frequency plots first before you bother with ADEV. These
> strip chart plots better show your raw data and measurement. Even a single
> glitch will be visible. Only if these plots are "clean" should you go ahead
> and use ADEV. Another trick is using the TimeLab "Trace" feature which
> splits the data into N segments and computes ADEV for each one
> independently.
> But in this particular case where you are comparing two GPSDO a phase
> difference plot will likely be more informative than an ADEV plot anyway.
> You may also want to play around with the averaging value (command 'g').
> /tvb
> ----- Original Message -----
> From: "GandalfG8--- via time-nuts" <time-nuts at febo.com>
> To: <time-nuts at febo.com>
> Sent: Sunday, March 19, 2017 9:08 AM
> Subject: [time-nuts] ADEV query Timelab and TICC
> > Yesterday I used one of John's excellent TICC modules for the first  time
> > and initially set up a quick test using the 10MHz output from a
> Thunderbolt
> > as the frequency reference to measure the 1PPS from an  Oscilloquartz
> Star4
> > GPSDO, with the TICC output feeding a USB3 port on a Windows  10 PC
> running
> > the 64 bit version of Timelab 1.29.
> >
> > I'll attach a copy of the test plots I'm referring to but just in  case
> > this doesn't get through I've also uploaded it to....
> >
> > https://www.mediafire.com/?9bue90yp1e8ueu6
> >
> > Using the basic settings as described in the TICC manual the first  run
> was
> > for 1 hour and seemed fine so I decided to extend the run time to 6
> hours.
> > The first 6 hour test started to follow the 1 hour plot as expected and I
> > watched this on and off and can confirm it did so up to somewhere between
> > the 100s and 1000s points on the x-axis, but some time after that the
> > complete  plot shifted upwards and then continued to completion to
> produce the
> > magenta  trace.
> >
> > I wasn't watching when it shifted so don't know if it was a jump or a
> > gradual shift but did see it continue until completion. When I repeated
> the 6
> > hour test, again without changing anything, and hoping to observe the
> effect
> > as it happened, it produced the green trace which was what I'd been
> > expecting to start with. Since then I've made other test runs and again
> all  seems
> > to be as expected.
> >
> >
> > Throughout the tests I have been simultaneously streaming data  from the
> > Star4 to Lady Heather via a "proper" serial port on the same PC so did
> wonder
> > if there might be some form of data conflict but it doesn't seem to  have
> > shown up as any obvious form of corruption and hasn't repeated  itself.
> >
> > Nigel,  GM8PZR
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