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

From: Tom Van Baak <>
Date: Wed, 4 Jan 2006 12:55:57 -0800

> The majority of such clocks only run the receiver for some part of
> the day to save power.
> One particular kind I examined ran the receiver until it had sync,
> then powered the receiver down for 23 hours and repeated the cycle.

Yes, but the LS bit stays lit for the entire month (at
least for WWVB) so the RC clock has plenty of notice
to insert a leap second at the end of the month if it
wanted to, regardless of reception quality the day
of the leap second.

Unfortunately, this is not the case with the DST bits.
Users routinely complain that WWVB RC clocks do
not handle DST correctly. This is because there is
less than one day advance notice of a DST change.

Given that most RC clocks only tune in late at night
(e.g., 11 PM), unless one has perfect reception in the
few hour window between 11 PM and 2 AM, a WWVB
RC clock won't make the DST switch in time.

To me this is a broken design, but I can't see it being
fixed anytime soon. The right way is something like a
DST count-down field (perhaps at least 3 bits wide).

Are there some LF broadcasts that announce DST far
enough (many days or weeks) in advance that the time
change can be done reliably?

Received on Wed Jan 04 2006 - 12:59:13 PST

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