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

Poul-Henning Kamp phk at phk.freebsd.dk
Wed Feb 7 02:13:10 EST 2018

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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