Hal,
THe Spectracom receiver is actually very good. It can pull the signal
from beneath the noise (literally), but doesn't do well with cochannel
signals. What I saw on the scope was a substantial carrier modulated
with 60-Hz square wave(!). That's why I suspect an arc welder. I called
in the power company and they were quite cooperative (heck; they were
hams themselves). It was easy to verify the crud quickly dived under the
noise when more than a couple hundred feet from the power line. I could
probably fix it at home with line filters.
Outboard DSP might help, but I would DC coupling and the only thing I
have around for that is an old DSP93. Heck; not this year.
Dave
Hal Murray wrote:
The WWVB signal has become degraded in recent years and now all WWVB
receivers here have been retired. Here in Delaware we are on the 100
microvolt per meter contour (before the WWVB transmitter upgrade) and
normally this would be sufficient for good accuracy. However, at least
here in Newark, there is another strong signal on 60 kHz that interferes
with WWVB. I chased this down to power-line conducted EMI and found the
interferiing signal was well above the noise several miles from campus.
It's not clear where it originates, but the prime suspect is a power
inverter for an arc welder at the Chrysler plant in town.
I'm not a wizard at this stuff. CPUs are cheap these days.
Would it be possible to pull the signal out of the junk
with some serious DSP hacking?
At the back of an envelope level, how would one answer
that question?
On the other hand, NIST recently upgraded the transmitter
at WWVB, so somebody must think this is a valuable service.
Do they have anybody tracking the EMI issues?
Who uses WWVB these days? Have serious time hackers all switched
to GPS, leaving "atomic clocks" as the only customer?
_______________________________________________
questions mailing list
[email protected]
https://lists.ntp.isc.org/mailman/listinfo/questions
