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

Bob Camp lists at rtty.us
Wed Mar 20 07:30:37 EDT 2013


Hi

So far all the WWVB stuff is running here. That includes my Casio wristwatch. I admit that this thread convinced me to actually check it….

Bob

On Mar 20, 2013, at 2:34 AM, Bill S <biltime at gmail.com> 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.
> 
> 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-**of-radio.html<http://ka7oei.blogspot.com/2013/02/did-nist-break-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-nist-did-break-bunch-of-radio.html>- The testing with the WWVB simulator
>>> 
>>> 73,
>>> 
>>> Clint
>>> KA7OEI
>>> 
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