[time-nuts] WWVB clocks no longer lock (Was: Used Spectracom)

[Clint Turner]

At about the time WWVB announced switching the format, two of my clocks 
- identical "SkyScan" units bought at about the same time 10 or so years 
ago suddenly stopped synchronizing, too.  If just one of these clocks 
had a problem, I would chalk it up to a random failure - but two of them?

One of these clocks is in my ham shack, next to a different model clock 
(one displays UTC, the other local) and this other clock hasn't missed a 
beat while the other is on the wall, well away from any noisemaker like 
a switcher or a CFL.  I've actually swapped these clocks and neither one 
is happy.  I've also put a different brand clock in its place and it 
maintains synchronization just fine.

I've checked for noisemakers (switching supplies) and found a noisy one 
- and then quieted it down with added filtering, but even before I did 
this it hadn't affected a clock only a few feet away from it!

The *only* time that these clocks lock up is when I first install the 
battery, but from then on they claim to be locked, but are drifting away 
from proper time.

For one of these, I popped the cover and found the trace with the WWVB 
time code from the die-mounted receiver chip and it looks pretty clean:  
No "stuttering" is apparent, but I didn't make any attempt to time every 
type of mark or space to verify its timing.

The fact that it synchronizes just once is puzzling - as is the fact 
that just this particular model is now unhappy:  Was even a minor change 
made to the AM portion of the code?  I could imagine that a too-narrow 
bandpass filter could slightly affect the timing of the pulses as the 
phase flipped, but even if this were the case, why does it always 
synchronize just the one time and then never again?

'Tis a puzzlement...

73,

Clint
KA7OEI



J.L. Trantham wrote:
> I have two 'cheap' WWVB 'Atomic Clocks', both of which say they are 'locked'
> and are about 2 minutes apart.
>
> Joe