[time-nuts] Setting loop TC using thunderbolt internal data.

Bruce Walker bruce at w1bw.org
Mon Jan 26 15:24:08 EST 2009


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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