[time-nuts] Thunderbolt E failing

[Adrian Godwin]

But doesn't the compensation help generate a feed-forward term, a way to
make the integrator better managed ?

On Sun, Sep 13, 2020 at 2:31 PM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> The point is that there is no need to compensate the part while it is
> locked.
> It meets all the specs required of it by virtue of the lock to GPS. The
> big issue
> on these devices ( = cell tower GPSDO’s) is holdover. That’s where all the
> magic comes in.
>
> Indeed, trying to compensate *and* learn at the same time generates even
> more issues to deal with. The temperature effect is not a simple linear /
> first
> order sort of thing ….
>
> Bob
>
> > On Sep 13, 2020, at 1:41 AM, Matthias Welwarsky <time-nuts at welwarsky.de>
> wrote:
> >
> > On Samstag, 12. September 2020 23:53:39 CEST Bob kb8tq wrote:
> >> Hi
> >>
> >> As far as anybody knows (which *is* a big qualifier indeed ….), the
> TBolt
> >> family only does it’s “temperature compensation” stuff when it’s in
> >> holdover. While it’s locked, there *appears* to be no compensation being
> >> done. If it’s doing anything while locked, it’s learning what the TC
> is, so
> >> it can use that information while in holdover.
> >
> > That is interesting, why wouldn't they use the information if it's
> available?
> > Watching the temperature gives you a prediction of what is going to
> happen,
> > while watching the phase only shows what has already happened. And
> knowing
> > what's about to happen is always very favorable in control theory.
> >
> >>
> >> Bob
> >>
> >>> On Sep 12, 2020, at 3:52 PM, Matthias Welwarsky <
> time-nuts at welwarsky.de>
> >>> wrote:
> >>>
> >>> Kevin,
> >>>
> >>> how long has it been in storage? I expect the GPSDO doing quite clever
> >>> things to compensate for temperature effects. There may be some
> >>> parameters stored on the device and the characteristics of the OCXO may
> >>> have changed after being turned off for an extended period.
> >>>
> >>> Regards,
> >>> Matthias
> >>>
> >>> On Samstag, 12. September 2020 18:13:35 CEST Kevin Schuchmann wrote:
> >>>> Matthias,
> >>>>
> >>>>   You are correct, having spent hours looking at all the stable areas
> >>>>
> >>>> and cooling and heating the gpsdo I find that when it reports that it
> is
> >>>> 116.25 F then it is stable.
> >>>> So now I guess I need to figure out why it is so picky. I will measure
> >>>> the current draw from a cold start and see if I see the oven warming
> up
> >>>> and then stabilizing and then heat and cool it and see how it reacts,
> >>>> and also look at the electronics and see if an area is overly
> sensitive
> >>>> to temperature.
> >>>>
> >>>> Thanks
> >>>> Kevin
> >>>>
> >>>> On 9/11/2020 2:26 AM, Matthias Welwarsky wrote:
> >>>>> On Freitag, 11. September 2020 01:08:09 CEST Kevin Schuchmann wrote:
> >>>>>> Guess my image didn't make it, I will add it as an attachment this
> >>>>>> time.
> >>>>>
> >>>>> The temperature curve seems to show some correlation to what is
> >>>>> happening
> >>>>> with the DAC. Seems that the DAC and OSC jumps are mostly during
> periods
> >>>>> of some thermal perturbation.
> >>>>>
> >>>>> Regards,
> >>>>> Matthias
> >>>>>
> >>>>>
> >>>>>
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> >
> >
> >
> >
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