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

Deirdre O'Byrne deirdre.dub at gmail.com
Wed Feb 7 07:53:56 EST 2018

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.

[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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