[ntp:questions] Re: Comparing offset of multiple refclock/servers

Hal Murray hmurray at suespammers.org
Tue Aug 16 16:19:56 UTC 2005

>Consider the case of conducted RFI, which  was originally targeted at CB 
>receiver local oscillators leaking into the power line. Consider also 
>the case where some high power welding machine at 60 kHz backs up into 
>the power grid. FCC 15.207 says not more than a millivolt can leak into 
>the power line. You're telling me a 500 kW welding machine leaks less 
>than a millivolt at 560-V three-phase AC source? What say the Chrysler 
>management if I show up at their front door with a field strength meter 
>pegged at 60 kHz? Heck, the FCC consultants told them BPL wouldn't work, 
>but nobody was listening.

NPR's Morning Edition had a story on BPL this morning.  They
mentioned interference with hams.  I don't remember anything
about interference with timekeeping.

Back to UPSs.  It might be interesting to try a measurement near
the ones that don't cause problems.  My guess is that they are
trashing some other frequency.  60 KHz is pretty old for switching
power supplies.  Small ones are in the MHz now.

Another thing to keep in mind is energy saving flourescent lights.
They often run at 50 KHz.

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