Roy Lewallen wrote:

I played with that many, many moons ago. The bugaboo is local noise --
QRM from all kinds of devices running from mains power, switching,
arcing, and sparking. The noise was lower late at night when more
gadgets were off, which I'm sure is why the automatic clocks you can get
now do their synchronizing late at night. So I suggest looking at each
architechture for its noise immunity and how it responds when it does
get a burst of noise. Absolute minimum bandwidth is an advantage from a
noise standpoint, as long as it's not so narrow that it rings for too
long when hit with an impulse. A PLL with long loop time constant might
be a good idea, since it should maintain synchronization through a noise
burst. Other than those generalities, I don't have much to offer. I
built up a simple receiver long ago that allowed me to see the binary
code on a scope, but only late at night. I never pursued perfecting it
to the point where it would be reliable. WWVB increased its power
between then and now, but it's probably still not a piece of cake.

Roy Lewallen, W7EL

Joel Kolstad wrote:
I've been thinking about building a WWVB (time code on 60kHz) receiver, and
wanted to get some suggestions for the architecture. Poking around the web
some, I did find one receiver where the guy built a synchronous detector
using a PLL and VCXO to phase-lock to the 60kHz carrier. Nice idea --
especially since he wanted the 60kHz carrier as a synchronization signal.
However, I just want the time data... so... wouldn't it be easier to build a
mixer at, e.g., 59kHz and then use an envelope detector to get a loud/quiet
audible (1kHz) tone (WWVB reduces power by 10dB to signify 0 bits in its
time code)? It seems to me that this approach avoids the need for the PLL
and VCXO, which is a nice 'reduction' in complexity. Also, since I'll have
a microcontroller around to decode the time code anyway, it can easily
generate the 59kHz signal.

Thanks,
---Joel Kolstad



I get a good signal into central Florida these days. I could barely
pick them up before they replaced their antennas and upgraded the
transmitters. I could pick up the harmonics of the horizontal sweep of a
TV set over a half mile away, but WWVB was so weak it was wiped out by
power line noise and other VLF noise. Temic makes a single chip
reciever/decoder, but I don't know if it is available in small
quantities. I have the data sheets, but I have to look for them.
--


Michael A. Terrell
Central Florida