[time-nuts] WWV Clock
Mike Monett
xde-l2g3 at myamail.com
Mon Nov 2 08:50:35 UTC 2009
"Majdi S. Abbas" <msa at latt.net> wrote:
> On Sun, Nov 01, 2009 at 05:51:24PM -0500, Glenn Little WB4UIV
> wrote:
>> My WWV clock at home and the master clock at the TV station that
>> I am engineer for did not update to EST from EDT.
>> Did anyone else see their WWV clock not change time for DST?
> WWVB does have a bit that accounts for it, but most of those
> clocks just try to update once a day, and if they take a single
> bit error in the minute or two they check, they'll miss it.
[...]
> Majdi, N0RMZ
I don't know if WWV receivers work this way, but WWVB clocks start
looking at midnight and repeat every hour until 06:00, or until they
get a valid signal. Once they update, they no longer look for the
time signal until the next midnight.
If the signal is strong enough to update at midnight, the clock will
miss the time change at 2:00 am. So they will be off by one hour
until the next update.
In this case, the problem is not due to a weak signal causing a
single bit error, it is due to a strong signal and receiving all the
bits correctly on the first attempt.
In my case, the GCD distance between Toronto and Fort Collins is
1333 miles (2144 km, 1158 nautical miles), and the direction is
269.6 degrees: <http://www.indo.com/distance/>
The NIST WWVB Coverage maps show the signal in Toronto is good at
0000UTC, and the receiver will probably synchronize on the first
attempt at midnight (0500UTC):
<http://tf.nist.gov/stations/wwvbcoverage.htm>
So all my WWVB clocks missed the time change on the first day. For
reference, the clocks are HTAWI HAA-1203W 12" White Atomic Analog
Wall Clock:
<http://www.partshelf.com/ps-haa-1203w.html>>
They have been on sale for $14.95 for several years, and I can
recommend them highly. Good styling, very economical, and excellent
reception. When I first got them, I was amazed to see them
synchronize at 5:00pm local time when the signals are very weak in
Toronto. The only problem is they make a loud tick every second,
which is the same as any digital clock movement. One day I will take
them apart and put a small resistor and speedup capacitor in series
with the motor to quiet them.
Regards,
Mike Monett
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