Re: [amsat-bb] Leap Second caution

Craig Mellinger (
Sat, 02 Jan 1999 20:28:30 -0500

Rick Walter wrote:
> Hi Jim.  I have the Radio Shack "Atomic Clock" and it has been right on
> since they first started selling them.  I watched my clock on New Year's
> Eve, and it updated correctly with the leap second added.  It has been
> right on ever since.  The Radio Shack clock updates at 9:00 PM local time.
> Since the extra second was added at 6:59:59 PM, local time (Eastern
> Standard) on December 31, I watched at 9:00 PM local and the leap second
> was added correctly.
> I went outside to watch my GPS receiver's time and it already had the leap
> second added before 6:59:59 PM local (0 hours UTC).  I'm not sure when
> that change occurred.  I have the Garman 45XL. Maybe the clock on the GPS
> receiver does not really come from the satellite's atomic clock?
> Did you notice most of the television shows counting down to the new year
> did not have the correct time due to the leap second?  They were all a
> second too fast! Also, I know many "accurate time" TV and radio stations
> are usually off a few seconds.  I've seen the weather channel be off by as
> much as 15 seconds.  That time may be generated locally, with the local
> forecast clock?
> Rick, WB3CSY
> On Sat, 2 Jan 1999, Jim S wrote:
> > A word of caution from personal experience for those of you using the new
> > "atomic" clocks to obtain accurate time for your satellite listening
> > and/or viewing pleasure.
> >
> > These clocks receive radio transmissions from WWVB to initially set and
> > periodically update themselves, applying an error correction to adjust or
> > fine-tune the internal time-base.
> >
> > The addition of a "leap-second" on January first confuses the clock into
> > adjusting for the apparent one-second error by making an unwanted
> > adjustment of the time-base rate.  If left alone, this should
> > automatically re-adjust itself back to a correct value over an extended
> > period of time.  In the interim, clock accuracy suffers.  If in doubt,
> > the clock should have a "reset" button hidden away somewhere which will
> > force the processor to return to default and start over.
> >
> > I was impatient and forced a reset so I cannot guess as to how long an
> > automatic resync would take.  I can say that the effects of the
> > leap-second adjustment were quickly apparent when compared to another
> > clock with only manual adjustment.
> >
> > Happy New Year!     ;)
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