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

Ruslan Nabioullin rnabioullin at gmail.com
Tue Feb 6 15:05:29 EST 2018

On Tue, Feb 6, 2018 at 2:37 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> If you look in http://phk.freebsd.dk/phkrel/NTPns.20080902.tgz
> you will find a file called dcf77_blame.c with my code,
> here is a couple of the simpler tests:
>         /* LSB of minutes must be different from previous minute */
>         j = ip->shiftprev[(offset + 21) % 60];
>         if (j * ip->shiftreg[(offset + 21) % 60] > 0)
>                 FAIL((why, " 0"));
>         /*
>          * If the LSB of minutes was '1' in previous minute
>          * the next higher bit must have changed, if it was
>          * a '0' it must not.
>          */
>         if (j *
>             ip->shiftreg[(offset + 22) % 60] *
>             ip->shiftprev[(offset + 22) % 60] > 0)
>                 FAIL((why, " 1"));
> ...
> I did a parallel prototype for MSF, but I didn't need it
> so I never completed it, not sure I have it around any
> more.
> I should really write an article about that code...

How difficult would it be to complete these modules and integrate them
with the rest of NTP, as NTP decoder modules?  So instead of an AM HF
receiver, the setup for these signals would be:

LF receiver set to CW demodulation set to appropriate parameters ->
NTP timekeeping system sound card

One of my organization's projects consists of robust public time
transfer via NTP over the Internet, based on a combination of various
on-site standards (rackmount OCXO, rubidium, and/or cesium standards)
and external signals (incl. WWV and CHU, using preamplifier ->
preselector -> analog parametric demodulator -> sound card, controlled
by ionospheric prediction daemon software on GNU/Linux via GPIB), the
nodes being geographically dispersed throughout the US and Canada.
It's probable that I will end up relocating to Western Europe
(coincidentally, the Republic of Ireland!) in the moderate future, and
therefore it would be nice if these LF or HF signals were to be
supported, for use as fallbacks to the standard GNSS sources (each
site typically will have one military and one industrial civilian
rackmount GPS receiver).


Ruslan Nabioullin
Wittgenstein Laboratories
rnabioullin at gmail.com
(508) 523-8535
50 Louise Dr.
Hollis, NH 03049

More information about the time-nuts mailing list