[time-nuts] crystal oscillators & TPLL

[Steve Rooke]

On 23 June 2010 03:29, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> In message <8F43D37E769B4CAAB3309830E40DD0A2 at Warcon28Gz>, "WarrenS" writes:
>
>>That is really all there is to it, if one starts with Frequency differences,
>>like the TPLL, and not Phase, like most other methods, to get the raw data
>>to use with an ADEV program like "PLOTTER".
>
> While it is absolutely true that you can calculate ADEV from frequency
> measurements, you have a very tough row to hoe when it comes to proving
> that your frequncy samples represent the same signal as a sequence
> of zero deadtime period measurements would do.

Well, it is zero dead-time because all differences between the
oscillators are continuously integrated into the output. There is no
period where the PLL is disconnected so as to induce bias into the
result.

> The time-delay inherent in any PLL really, really, really mucks the
> math up in that respect.

I understand the point you are trying to make here but this is a Tight
PLL implementation with the loop bandwidth much greater than the
minimum sampling period. Maybe that does complicate the math but the
concept is sound as there is no difference in this part of the method
than in the original NIST paper describing methods of frequency
measurement.

> With that said, I'm really, really, really sick and tired of this
> TPLL thread.

There is always the 'Del' key if you do not wish to contribute to
this, otherwise please do not complain.

Steve

> Poul-Henning
>
>
> --
> 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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-- 
Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at once.
- Einstein