[time-nuts] WWVB Clocks don't sync anymore (revisited)
biltime at gmail.com
Wed Mar 20 02:34:19 EDT 2013
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.
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.
> 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
>> bunch-of-radio.html<http://ka7oei.blogspot.com/2013/03/yes-nist-did-break-bunch-of-radio.html>- The testing with the WWVB simulator
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