[time-nuts] Radio Controlled Clocks

[Andy Talbot]

No, my GPS clock has it's own timekeeping function, complete with  leap
years and automatic DST setting, clocked from the 1 PPS signal.   All
running in a PIC 16F628  (It uses a Nixie tube display, because I just
happened to have some tubes !) The timekeeping registers are updated every
minute from GPS at the 58 second epoch.  As the NMEA stream carries the
data for the PPS that has *just happened*, then apart from start up,  it
will normally be writing to registers that already contain the same
information.

The only thing that will go wrong is at leap send insertion where it will
indicate the wrong time for 58 seconds after midnight - I don't care about
that.   Suppose I could do the GPS read and update at the :00 second point
which would repair leap seconds for all but the 23:59:60 interval, but it
'felt wrong' to do that at the time of writing the code.

Andy
www.g4jnt.com



On Sun, 27 Dec 2020 at 18:12, David G. McGaw <david.g.mcgaw at dartmouth.edu>
wrote:

> A clock that uses an NMEA stream for its display will be a few hundred
> milliseconds slow, dependent on the chosen data products and serial baud
> rate, as NMEA gives the time of the previous second mark.
>
> David N1HAC
>
> On 12/27/20 9:54 AM, Andy Talbot wrote:
> > I've just had a look around the house, and actually have four MSF clocks
> > and an old wristwatch minus its strap (antenna is a small ferrite rod
> > inside).  Forgot I had an old Junghans one as well - that is sitting out
> in
> > the shed as it requires a stronger signal than the more modern ones, and
> > seems to get better reception out there.   It's the only one that shows
> MSF
> > outages as it updates every hour - and the battery seems to last forever!
> >   I never checked to see how close that is to GPS;  if they implement
> proper
> > timing or just a simple delay bodge.
> >
> > Andy
> >
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> >
> >
> > On Sun, 27 Dec 2020 at 14:02, Peter Vince <petervince1952 at gmail.com>
> wrote:
> >
> >> Hello Andy,
> >>
> >>       I have an old Maplin digital LCD clock for MSF, and that is always
> >> about a second slow, but the Coopers analogue clocks are MUCH closer,
> as is
> >> the Junghens DCF digital LCD clock.  But the Junghens DCF clock always
> >> misses one or other of the DST changes!
> >>
> >>       Peter
> >>
> >>
> >> On Sun, 27 Dec 2020 at 12:11, Andy Talbot <andy.g4jnt at gmail.com> wrote:
> >>> With this talk of Radio Controlled clocks...
> >>> I have three domestic RC clocks here, receiving the UK 60kHz signal,
> MSF.
> >>>    However, I notice that when compared against a GPS clock, timed from
> >> the
> >>> 1 PPS signal & NMEA output, they all are a few hundred milliseconds
> fast,
> >>> ie the display changes just before the GPS derived time.
> >> ...
> >> ...
> >>> I only ever have digital display clocks, so wouldn't know if the same
> >>> happens with round ones with hands.    Anyone else using domestic MSF
> or
> >>> DCF77 clocks who have observed this?
> >>>
> >>> Andy
> >>>
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