One does not use the 100 Hz tone, one counts doubled ticks in
the first 16 seconds of each minute. Right now ticks 9, 10, and
11 are doubled, so DUT1 is -0.3 s. See
http://www.nist.gov/pml/div688/grp40/wwv_format.cfm#ut1
for more details.
I made an error when I wrote WWVB, I meant WWVH.
Of course, one would need optics to make solar or star observations,
when I said no equipment beyond a stopwatch, I meant no additional
timekeeping equipment beyond a shortwave receiver, which I thought
was a given for this discussion.
As for "Define "valid" then. If a government is spending taxpayer money
for a data service that citizens haven't used for decades", if indeed
citizens
haven't used it for decades, that would be a valid reason to drop it.
I'm just
saying that the absence of new commercial equipment to automatically
derive DUT1 from WWV or WWVH does not prove that no one is obtaining
DUT1 from those stations.
On 8/4/2011 9:45 AM, Tom Van Baak wrote:
It is not necessary, at least in the case of WWV and WWVB, to have
special
equipment beyond a short wave radio to decode DUT1. It can be done by
ear.
In 1975 short-wave radios were common, but today a short-wave
radio qualifies as "special equipment".
Even with a SW radio, when was the last time you listened to the
*subcode* of WWV? These are not the famous 1 second ticks
we're talking about; it's the low 100 Hz audio tone that is hidden
below the ticks. It often takes quality headphones or instrument
grade SW radio to hear this. The subcode doesn't come through
on the cheap plastic handheld SW radios.
As for WWVB, that's a LF transmission (60 kHz) not short-wave
and there's no audio to hear. WWVB receivers are plentiful (in
so-called atomic clocks and watches), but none of them decode
DUT1.
Timings of sun and star observations can be done with a hand-operated
stop watch to a precision of 0.1 s, the same precision as DUT1. (Not
to say there won't be personal errors in excess of 0.1 s, but those
errors
will probably be well under 1 s.)
Can you send me a link describing this procedure. I'm surprised
it can be done with just a stopwatch and no optics.
I suspect the other reasons to drop DUT1 will be persuasive, but the
lack
of commercial decoders is not a valid reason to drop it.
Define "valid" then. If a government is spending taxpayer money
for a data service that citizens haven't used for decades, then it
seems to me there is some validity for dropping the service. Or,
at least replacing that vintage service with something modern.
You can get DUT1 on the web now with 1000x greater precision
of WWV/WWVB.
/tvb
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