[time-nuts] New Subscriber, DIY GPSDO project (yes, another one)

[Bob kb8tq]

Hi

If you go that way, just run a pure FLL for the “main loop” and do the phase
on top of that. Assuming you are disciplining an OCXO, it works pretty well ….
Even more so if you keep time tagged phase ( to do frequency from phase) 
and can look at some very long tau “frequency” as a section of the loop. 

Bob

> On Mar 9, 2020, at 9:44 AM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> 
> --------
> In message <1593455.IjMom2WFaZ at linux-5fgm.suse>, Matthias Welwarsky writes:
> 
>>> Backing up a bit …. the objective is not to minimize overshoot or
>>> keep the loop from oscillating. The issue here is optimizing the noise
>>> output of the combination of GPS + OCXO when combined via
>>> the control loop. It’s a very different objective ….
>> 
>> Absolutely. The GPS will introduce a ton of noise and the objective for the 
>> control loop is mainly to keep the influence of this noise away from the GPSDO 
>> output for small tau. You want the GPS only have an influence for large tau, 
>> ideally only countering the aging of the LO.
> 
> Has anybody ever played seriously with separate frequency and phase
> adjustments ?
> 
> I'm thinking 24h (to minimize GPS periodicities) frequency measurement
> and adjustment, with a continuous very weak proportional phase adjustment
> to come with measurement noise and rounding errors ?
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
> 
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