[time-nuts] Re: GPSDO replacement recommendation

[Matt Huszagh]

On Fri, Apr 19, 2024 at 9:21 AM Ole Petter Ronningen via time-nuts
<time-nuts at lists.febo.com> wrote:
>
> The trick to getting good adev based on a Mosaic-T GPSDO is to simply
> bypass the whole sawtooth problem. Dont compare the PPS from the Mosaic-T
> with a PPS derived from your steered oscillator, rather run the Mosaic-T
> with the steered 10MHz directly, and use the relevant messages from the
> Mosaic-T to run the control loop. No external phase-detector necessary, no
> PPS sawtooth to struggle with. It is described in the hardware manual for
> the mosaic, appendix D.
>
> ADEV of 2e-13 at 1s on the steered clock (OCXO) has been demonstrated this
> way, although with Atomichron real time PPP - but the architecture should
> work either way. YMMV.

2e-13 at 1s was intentional, right? Do you have any further details on
this? The PPS ADEV of GNSS receivers such as the ZED-F9T is almost 5
orders of magnitude worse than 2e-13 at 1s. So, normally, you'd need this
stability to come from the OCXO. As far as I know, it takes a really
good OCXO to get 2e-13 at 1s.

Matt