[time-nuts] Thunderbolt E failing

[Bob kb8tq]

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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