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

[Magnus Danielson]

Hi,

You probably want a long-time-constant steering of the FLL from the
phase, to make sure any residue frequency offsets and low-frequency
parts keeps the phase-control within range.

Cheers,
Magnus

On 2020-03-09 15:04, Bob kb8tq wrote:
> 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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