[time-nuts] WWV Clock
brooke at pacific.net
Mon Nov 2 15:50:25 UTC 2009
Note that the way a clock checks to see of it has received the data correctly
is to compare two adjacent frames and check to see that they differ by one minute.
If the clock was smart it would start to listen a few minutes prior to midnight
and would recognize that there was going to be a DST change at midnight.
If the clock started at what it thought was midnight, but it was running a
second slow then it would miss the first frame, but the next minute it would
get the "new" frame and switch to/from DST.
I think your clock is just not receiving a good enough signal. The key may be
you need to mount the clock on a wall that's 90 degrees from where it is now.
That's the problem I had with an atomic clock, i.e. the loopstick antenna has
deep nulls and if you point the null at the transmitter . . . See:
I like the projection clock in my bedroom. No glasses, no light needed to tell
Mike Monett wrote:
> Replying to my own post, there are two bits that indicate daylight
> saving time changes. Here's a paragraph from page 27, Lombardi,
> "NIST Time and Frequency Services", NIST Special Publication 432,
> 2002 Edition:
> "Daylight saving time (DST) and standard time (ST) information is
> transmitted at seconds 57 and 58. When ST is in effect, bits 57 and
> 58 are set to 0. When DST is in effect, bits 57 and 58 are set to
> "On the day of a change from ST to DST bit 57 changes from 0 to 1 at
> 0000 UTC, and bit 58 changes from 0 to 1 exactly 24 hours later. On
> the day of a change from DST back to ST bit 57 changes from 1 to 0
> at 0000 UTC, and bit 58 changes from 1 to 0 exactly 24 hours later."
> So it seems the HTAWI receives the bits correctly, but it does not
> act on them until both are the same.
> Some relevant articles are available:
> NIST Special Publication 432, 2002 Edition
> NIST Special Publication 250-67
> WWVB RCC Recommended Practices 2009
> Mike Monett
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