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

David L. Mills mills at udel.edu
Wed Aug 17 01:40:58 UTC 2005


We radioteers are not the only ones hollering; FEMA was hot until the 
Feds reminded them the agency was one of them.

The quiet UPSes in my home are in the same house with sensitive HF 
receivers and awesome antennas. I took a LW radio in the machine room 
and it literally screamed at 60 kHz. I know about the flourescents, but 
that's not their scream.


Hal Murray wrote:
>>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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