[time-nuts] WWVB Clocks don't sync anymore (revisited)

J. Forster jfor at quikus.com
Wed Mar 20 12:24:12 EDT 2013


Have you tried to put BPSK through a narrow band filter and looked at the
envelope at the output?

-John

==========



> Hi
>
> Also consider that some of these receivers use a narrowband crystal filter
> in front of the IC. I doubt they spend a ton of money on the components,
> so
> that may not be the world's best crystal in terms of aging. If it ages far
> enough the receiver simply goes deaf. If it ages a bit less than that, it
> slices off one sideband much more than the other. That's likely to do all
> sorts of odd things to it's ability to ignore phase modulation.
>
> Bob
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Herbert Poetzl
> Sent: Wednesday, March 20, 2013 10:58 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] WWVB Clocks don't sync anymore (revisited)
>
> On Wed, Mar 20, 2013 at 02:34:19AM -0400, Bill S wrote:
>
>> Interestingly, I have three timepieces that will no longer
>> synch to wwvb.Two Radio Shack digital clocks and a Casio
>> wristwatch that I've worn for a couple of years and was always
>> pretty much dead on. Like Paul, I have an analog Lacrosse clock
>> that is running correctly. Nothing I've tried will make the
>> other clocks synch.
>
> Maybe this is related to the phase modulation time code
> protocol used by WWVB since October 29th, 2012.
>
> Their website also states that clocks using information
> from the carrier will no longer work, and that during the
> transition period (at least March 21st 2013), the PM
> signal will be turned for for 30 minutes twice a day
> (noon and midnight MST) so maybe check if the clocks
> sync then?
>
> best,
> Herbert
>
> http://www.nist.gov/pml/div688/grp40/wwvb.cfm
>
>> Bill_S W2FMA
>
>> On 3/19/2013 5:29 PM, paul swed wrote:
>>
>>> Funny you bring this up. I am just noticing a sharp clock that
>>> I always use and it has been accurate. But it did not flip
>>> with the time change this time and though it says its locked
>>> its off by 45 seconds slow. Yet a lacross clock across the
>>> room seems to be on second wise but never flipped with the
>>> time change. As I say its just becoming apparent. Regards Paul
>>> WB8TSL
>
>>> On Tue, Mar 19, 2013 at 4:55 PM, Clint Turner
>>> <turner at ussc.com> wrote:
>
>>>> A few weeks ago I posted a question/comment about some of
>>>> my WWVB-based "Atomic" clocks no longer setting themselves
>>>> properly. These two clocks, SkyScan #86716, would show the
>>>> symbol indicating that they had set themselves, but their
>>>> time was drifting away from UTC. Interestingly, they *would*
>>>> set themselves exactly once upon installation of the battery,
>>>> but never again.
>
>>>> Since that time, I've done a bit of digging around.
>
>>>> The first suspicion was that, perhaps, the NIST had fudged a
>>>> bit in the WWVB timecode recently, so I manually decoded a
>>>> few frames and analyzed them: Nothing suspicious there.
>
>>>> The next question was if the addition of the BPSK somehow
>>>> skewed the timing of the TRF's AGC/threshold - but logically,
>>>> this didn't make sense since the clock *did* set itself
>>>> exactly ONCE - and it wouldn't have been able to do this at
>>>> all were this the case. Out of curiosity I poked around on
>>>> the board and found the trace containing the time code and
>>>> found that despite the BPSK, its timing was exactly as it
>>>> should have been: No surprise there.
>
>>>> This left the clock itself, so I did what any other Time Nut
>>>> would do: I built a WWVB simulator.
>
>>>> Initially, I set it to a 2010 date - a time that I knew that
>>>> the clock worked properly. I had two clocks: One that I'd
>>>> just reset by pulling and replacing the battery while the
>>>> other had been "stuck" for a few weeks, not resetting itself
>>>> nightly as it should. I put both of these in the coupling
>>>> loops from my WWVB simulator and over the next few days, the
>>>> recently re-set clock happily synchronized itself while the
>>>> other one with the 2013 date was still "stuck." I then reset
>>>> that clock and it, too, behaved itself from then on.
>
>>>> I then reset the clock on the simulator to a February 2013
>>>> date and time. Initially, both clocks reset themselves to
>>>> the current time and date at their next midnight, but after
>>>> that, they got "stuck", never resetting themselves at "night"
>>>> again.
>
>>>> So, it appears to be a problem with "Broken Sand" (e.g. a
>>>> silicon problem).
>
>>>> For the morbidly curious, I have documented my efforts here:
>
>>>> http://ka7oei.blogspot.com/**2013/02/did-nist-break-bunch-**o
>>>> f-radio.html<http://ka7oei.blogspot.com/2013/02/did-nist-brea
>>>> k-bunch-of-radio.html>- The initial testing
>
>>>> http://ka7oei.blogspot.com/**2013/03/yes-nist-did-break-**
>>>> bunch-of-radio.html<http://ka7oei.blogspot.com/2013/03/yes-ni
>>>> st-did-break-bunch-of-radio.html>- The testing with the WWVB
>>>> simulator
>
>>>> 73,
>
>>>> Clint KA7OEI
>
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