[time-nuts] Setting loop TC using thunderbolt internal data.
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Mon Jan 26 20:36:43 UTC 2009
Bruce
What was the record length?
TOTDEV and TOTHadamard should give more reliable estimates over a
greater tau range.
Bias corrected Theo_1 and the Hadamard equivalent should be even better
at longer tau.
Bruce
Bruce Walker wrote:
> Thanks for the suggestion. Here is a composite plot with Allan and Hadamard
> deviations for my tbolt run last night with disciplining disabled. I think
> I computed Hadamard correctly.
>
> OADEV (blue) has a minimum of 9.6e-12 around tau=790
> OHDEV (red) has a minimum of 4.9e-12 around tau=1660
>
> --bruce W1BW
>
>
> On Mon, Jan 26, 2009 at 2:05 PM, Bruce Griffiths <bruce.griffiths at xtra.co.nz
>
>> wrote:
>>
>
>
>> Some idea of the shift in the minimum can be gleaned by plotting the
>> Hadamard deviation vs tau.
>>
>> Bruce Walker wrote:
>>
>>> I ran the same test as Bruce Griffiths on my tbolt; that is, I turned off
>>> osc disciplining altogether and created an OADEV plot from the internal
>>> phase measurements taken from its GPS solution. The plot is attached.
>>>
>> It
>>
>>> has a minimum of about 1e-11 at tau=800, and it has the sane general
>>>
>> shape
>>
>>> as Griffiths'.
>>>
>>> The next experiment I plan to do is to repeat the same thing using manual
>>> holdover mode rather than "Disable disciplining". That should continue
>>>
>> to
>>
>>> try to compensate for temperature and long-term drift (just not steered
>>>
>> by
>>
>>> GPS), whereas the data taken last night use a fixed DAC.
>>>
>>> --bruce W1BW
>>>
>>>
>>>
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