[time-nuts] Receiving the MSF time signal on cheap radio modules

Deirdre O'Byrne deirdre.dub at gmail.com
Wed Feb 7 14:15:43 UTC 2018


I've updated my paper, which now contains the attached graph. (I did a
linear regression analysis to see what the correction for the receivers
should be, and I applied receiver 2's correction to both receivers to
generate this graph).

So maybe a very cheap MSF disciplined oscillator might just work!? :o


[image: Inline images 1]

On 7 February 2018 at 12:53, Deirdre O'Byrne <deirdre.dub at gmail.com> wrote:

> Challenge accepted! And I thought this project was over :)
>
> My gnuplot skills are quite poor, but the two attached files tell a story.
> Yes there is a correlation between the length of the second and the
> "lateness" of the second pulse relative to UTC. BUT - the correlation is
> different between the two receivers.
>
> So one would have to characterise the receiver you were using.
>
> D.
> [image: Inline images 2][image: Inline images 1]
>
> On 7 February 2018 at 07:13, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
>
>> --------
>> In message <CAGJ4F+697SyXwm3yWG-XczN4zF7r2RAmXzAcEm=dhaqBJc_NNw at mail.
>> gmail.com>, "Deirdre O'Byrne" writes:
>>
>> >MSF disciplined oscillator?! I don't trust these receivers to any better
>> >than about the 20ms mark, so such a disciplined oscillator would have
>> quite
>> >a long integration time!
>>
>> It's actually more complicated and better than that.
>>
>> The low-pass filter dominates, so the falling flank at second N
>> depends on the pulsewidth at second N-1.
>>
>> I can't remember the numbers I got when I "sorted" DCF77 pulses depending
>> on the previous pulse being short or long, but it was a fair bit better
>> than 20ms.
>>
>> --
>> 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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