[time-nuts] crystal oscillators & TPLL

Steve Rooke sar10538 at gmail.com
Wed Jun 23 01:04:09 UTC 2010


I can see that you are somewhat frustrated with all of this but let's
please try to understand what is going on with the design and not get
bogged down with interpersonal issues.

On 23 June 2010 09:35, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> In message <415E11EFEC7B46FFB05A790F4F4A4D4D at Warcon28Gz>, "WarrenS" writes:
>>Poul-Henning posted
>>So is there some part that is not obvious to you?
> Yes, it is painfully obvious to me, that you are so in love with
> your idea, that no argument will ever penetrate your defensive
> shield.

This fact is painfully obvious to all of us but that does not mean it
is a bad thing, it's just that Warren is very passionate about what he
has done and he is obviously going to be defensive against anything
that he feels attacks his baby. It's not easy for anyone to share
their hard work for peer review and it really depends on the reactions
of the peers as to how the original submitter takes the feedback.

> Please look up the proper scientific response to your
> results in the following handy table:
> Observation                     Action
> ==========================================================
> Results worse than expected     Find out what went wrong.
> ----------------------------------------------------------
> Results as expected             Find out what went wrong.
> ----------------------------------------------------------
> Results better than expected    Find out what went wrong.
> ----------------------------------------------------------

Interesting table. Maybe you would have been more constructive in
saying that any experimental method has limitations and errors. These
need to be noted along with any results as they form part of the

Let's kick this off. The R/C filter which feeds off the PLL loop and
onto the ADC has a BW that limits measurements below 0.1s. The effect
of drift in the reference oscillator will affect the results of the
longer tau and test results show that the upper limitation seems to be
in the order of 100s. Now the reference oscillator could have it's
drift analysed over a period and so the effects of this could be
mathematically removed from the measurements thereby improving the
results and possibly extending the upper limitation.

One thing that we have to bear in mind is that any drift in the DUT,
say, if it is an xo, will result in "distortion" of any results for
long tau anyway as ADEV is not suited to handle oscillator drift. This
will cloud the measurement of some times of noise, like random-walk,
and this should be born in mind with any ADEV measurement

> Please do not reply to this email, I have no desire to
> have further correspondence with you.

Does that include me too?

Steve - another 'nix nut

> --
> 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

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