Re: [LEAPSECS] Diagram of CHU Leap-Second Recording and "Atomic" Clock

From: Tom Van Baak <tvb_at_LEAPSECOND.COM>
Date: Wed, 4 Jan 2006 12:03:27 -0800

It is correct that DUT1 changes by +1.0 across a
positive leap second; going from a negative value
(e.g., -0.6) to a positive value (e.g., +0.4).

You would see the inverse in the case of a negative
leap second (DUT1 will, by definition, be positive
before the negative leap second and go negative
after the leap).

As for the delay in implementing IERS bulletin D 92;
I was always under the impression that national
time institutions could implement this at their
convenience and, unlike leap seconds, did not
have to change the DUT1 bits at the precise day
and hour that IERS dictated.

Perhaps someone on the list from NIST or USNO
can clarify how this has been done in the past?

When you think of it; with DUT1 being broadcast
with a low precision of 0.1 seconds; there doesn't
seem to be any reason to expect every national or
local IRIG broadcast of DUT1 to make the change
with 1 minute, or 1 day, or even 1 month precision.

As for your Skyscan clock, I have several dozen
similar consumer RC clocks here and none has
ever adjusted itself for a leap second in real-time
(also try displaying :59:60 on an analog clock!).
They all get back in sync eventually, though.

That's a nice CHU capture. Thanks for sharing it.


----- Original Message -----
From: "Richard Langley" <lang_at_UNB.CA>
Sent: Wednesday, January 04, 2006 08:04
Subject: [LEAPSECS] Diagram of CHU Leap-Second Recording and "Atomic" Clock

> I recorded the audio of the 3330 kHz signal of the National Research
> of Canada's time signal station CHU from a few minutes before, until a
> of minutes after, midnight UTC on New Years' Eve. A PDF of the annotated
> sampled-signal time series between 23:59:00 and 0:00:01 can be found here:
> <>. The leap second
> correctly inserted. However, starting one minute after UTC midnight, DUT1
> became +0.4 seconds rather than +0.3 seconds as prescribed by IERS. The
> second value continued to be transmitted until some time on 3 January
> According to an NRC staff member, the problem arose because the IERS
> D announcing the +0.3 second value was not sent out until 28 December and
> was not seen until people returned to work on 3 January after the
> This problem seems to have occurred with some other time signal stations
> Simultaneous with the audio recording of CHU, I videotaped the display of
> SkyScan "atomic" clock, model 31981, marketed by Equity Time U.S.A., which
> receives the WWVB signal. It did not account for the leap second at UTC
> midnight. Likely it continued that way until it next tried to receive the
> signal.
> Richard B. Langley E-mail:
> Geodetic Research Laboratory Web:
> Dept. of Geodesy and Geomatics Engineering Phone: +1 506 453-5142
> University of New Brunswick Fax: +1 506 453-4943
> Fredericton, N.B., Canada E3B 5A3
> Fredericton? Where's that? See:
Received on Wed Jan 04 2006 - 12:06:56 PST

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