[time-nuts] Time-Nutters-- Adding Rubidium to a Thunderbolt...?

[Matthias Welwarsky]

On Dienstag, 3. März 2020 09:25:13 CET Dana Whitlow wrote:
> Matthias,
> 
> You said that the LPRO has a pulling range of 4 PPM.  Really?  I
> would think that 4PPB would be much more likely for a Rb.

Yes, sorry, typing mistake. The user guide says "more then +/- 1.5E-9", I 
found it more in the range +/- 2E-9". It's 4ppb, not 4ppm.

BR,
Matthias

> 
> Dana
> 
> 
> On Mon, Mar 2, 2020 at 3:21 PM Matthias Welwarsky <time-nuts at welwarsky.de>
> 
> wrote:
> > On Montag, 2. März 2020 18:32:44 CET Skip Withrow wrote:
> > [...]
> > 
> > > The Thunderbolt DAC steps in 10uV steps IIRC.  And it steps its DAC
> > > voltage every second.  With GPS signals jumping around you can still
> > > (will) end up with poorer short term performance than if the Rb was
> > > left to its own devices.  Hint, let the Thunderbolt do its thing with
> > > the Rb, but use Lady Heather and disable disciplining when making
> > > measurements/comparisons.
> > 
> > The LPRO has a pulling range of just 4ppm at the external C-Field input
> > (0-5V
> > swing). 10µV steps over 6V should be, like 19 bits or so? That should give
> > at
> > least 7e-15 resolution for the DAC.
> > 
> > With a reasonably stable PPS from a timing receiver, just looking at the
> > DAC
> > movements, it should not be a problem to have a MDEV of 1e-14'ish for
> > tau=1s.
> > The LPRO itself probably has a MDEV of somewhere between 1e-11 to 1e-10 at
> > tau=1s, so the GPSDO is not going to cause a lot of disturbance. Some,
> > yes.
> > The undisturbed Rb will always be better short-term than the disciplined
> > one.
> > But not an awful lot.
> > 
> > BR,
> > Matthias
> > 
> > > Regards,
> > > Skip Withrow
> > > 
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