[ntp:questions] Re: Spectracom 8170 question..
David L. Mills
mills at udel.edu
Fri Aug 12 21:49:57 UTC 2005
The antennas are about 200 feet away form the machine room and atop an
adjacent utility building. A check with a portable radio gave no
comfort; RFI levels are atrocious.
I have a Netclock/1 WWVB receiver at home working okay, but I also have
three 2200-VA UPSes, one less than four feet from the antenna. I
conclude that some UPSes radiate on 60 kHz and some don't.
Over the years RFI on 60 kHz has increased even without the UPS problem.
Several years ago I traced it to conductive interference on the power
line. Two engineers form the local power company came to the same
conclusion. Put a 60-kHz radio near a power line and it goes crazy; move
it 100 feet away and comforting silence. I could clearly see it on an
oscilliscope connecte to the synchronous detector in the WWVB radio; it
had a nasty modulation that made me think it a high power power inverter
for a welding machine. We do have a Chrysler plant in town.
I called the FCC monitoring station at Laurel, MD, and asked them to
take a look. They and the FCC Maine station concluded the radiation came
from somewhere in Quebec, so I would have to pursue the issue with the
State Deparment. My pals in Boston have no such WWVB problem. So much
for the FCC monitors; I suspect they will be closed down to protect the
As an aside, I've been at the FCC monitoring station in Washington, DC.
An old R-390, Teletype model 12 and a plotting board with string and
tacks. The FCC was on the way out of town last I heard. Did the last
engineer to leave the place douse the lights? Only lawyers are allowed
Hal Murray wrote:
>>Schematics are at http://www.eecis.udel.edu/~mills/database/8170/. You
>>can find the DIPswitch, eyeball the component ID and go find it on the
>>board. Send it T to wake it up. The * means it's not synchronized. I
>>hope you got the antenna/preamp; it doesn't work without it. Also be
>>aware the heavier UPSes produce so much RFI that we have had to stand
>>down both of our 8170s.
> How far apart are (were) the UPSs and the 8170s?
> Do the 8170s still work if you locate them somewhere nice or does the
> crap from the UPSs get back out on the power line and polute the
> whole area? (In which case the problem could be from UPSs in
> other buildings/organizations...)
> Do home size UPSs have the same problem? Perhaps killing the
> "atomic" clocks in the rest of the house? (The ones that set
> themselves from WWVB.)
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