[time-nuts] NIST

Bob kb8tq kb8tq at n1k.org
Mon Aug 13 07:59:10 EDT 2018


Hi



> On Aug 13, 2018, at 7:24 AM, Dana Whitlow <k8yumdoober at gmail.com> wrote:
> 
> Note to all;
> 
> Be cautious about getting time of day from consumer GPS products.  All that
> I have encountered
> (so far) exhibit T.O.D. errors up to a few tenths of a second, and the
> error is not repeatable from
> session to session.  Some do have PPS outputs, which are typically claimed
> to provide usec
> level of accuracy, but most do not.

… but there *are* modules out there for not a lot of money that do indeed give
quite good PPS (and TOD) information. Picking out the good brands / models
from the junk is part of why you have lists like this one. 

> 
> I routinely use WWV to verify correct setting of my WWVB-synced watch and
> kitchen clock.  I have
> occasionally seen severe setting errors, which I attribute to attempts at
> syncing in the face of poor
> WWVB reception conditions.
> 
> My impression is that none of the time codes currently in use by broadcast
> NIST time signals
> contain forward error correction or even error detection features.  If this
> is wrong, please somebody
> correct me!
> 

I believe you will find that the “new” PSK modulation scheme on WWVB has at 
least some error detection built into it. 

> BTW, there are a fair number of Heathkit clocks in the wild which use WWV
> (as opposed to WWVB)

There aren’t a lot of those left running these days …..

Bob


> for syncing.  An old college-era housemate with whom I keep in touch owns
> and still uses at least
> one of them.
> 
> Dana
> 
> 
> On Mon, Aug 13, 2018 at 5:25 AM, Mark Spencer <mark at alignedsolutions.com>
> wrote:
> 
>> I'm trying hard to think of routine users of WWV / WWVH other than amateur
>> radio operators, time nuts, and the occasional academic / scientific study
>> that uses the transmitters as a signal source.
>> 
>> Perhaps some boaters still use the time signals to set their chronometers,
>> but WWV /WWVH probably wouldn't be my first choice for that application if
>> I had access to GPS.
>> 
>> Perhaps some other users of the radio Spectrum occasionally use the
>> signals as a basic test signal ?
>> 
>> I use the time signals for my amateur radio hobby when I already have an
>> HF receiver and don't want to mess with using GPS as a time source.  I only
>> need accuracy within perhaps a third of a second so manually setting a
>> computer clock while listening to WWV works for me.
>> 
>> For my own interest I'd be curious in knowing of other routine uses of the
>> WWV / WWVH time signals.
>> 
>> 
>> Mark S
>> VE7AFZ
>> 
>> mark at alignedsolutions.com
>> 604 762 4099
>> 
>>> On Aug 12, 2018, at 2:08 AM, Bob kb8tq <kb8tq at n1k.org> wrote:
>>> 
>>> Hi
>>> 
>>> One would *guess* that stopping WWVB (and killing mom and pop’s “atomic
>> clocks”) would not be a reasonable thing to do.
>>> It gets a lot of voters mad. I doubt that very many voters (percentage
>> wise) would notice WWV and WWVH going away ….
>>> 
>>> Bob
>>> 
>>>> On Aug 11, 2018, at 9:00 PM, jimlux <jimlux at earthlink.net> wrote:
>>>> 
>>>> On 8/10/18 12:45 PM, Robert LaJeunesse wrote:
>>>>> I'd say it does get more detailed, with the $49M in cuts described
>> generally in groups here:
>>>>> https://www.nist.gov/director/fy-2019-presidential-budget-
>> request-summary/fundamental-measurement-quantum-science-and
>>>>> One item: "-$6.3 million supporting fundamental measurement
>> dissemination, including the shutdown of NIST radio stations in Colorado
>> and Hawaii"
>>>> 
>>>> I wonder if that's WWVB, or WWV & WWVH
>>>> 
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>>> 
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