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

[J. L. Trantham]

After reading the 'antenna on the ground' comment and being suspicious of
the 'upstairs' clock, I brought it down stairs, placed new batteries, and
sat it on the window ledge with the antenna 'broadside' to the west.  I then
went to the shop to putz around for a while.  After about an hour, I came
back to discover it had 'locked' (although EST instead of CST) and was 'dead
on' with the other, 'downstairs', clock.

I made the changes to the display needed and it is still 'right on'.

Must have been an ongoing signal issue, battery issue, or an interfenence
issue.  The 'upstairs' clock is oriented east/west and sits high on the
wall, over my office computer which is on most of the time.  No other source
of interference except winter and solar storms.  We'll see.

I'll move it back 'upstairs' and continue the 'watch'.  It is troubling that
it continued to give a 'locked' indication when, clearly, it was not.  I may
have to put a TBolt in my office.

Joe

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Clint Turner
Sent: Thursday, January 17, 2013 2:36 PM
To: time-nuts at febo.com
Subject: [time-nuts] WWVB clocks no longer lock (Was: Used Spectracom)

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


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