[time-nuts] power line common view - a silly experiment

[Kasper Pedersen]

I have servers at two sites: At home (northern part of Silkeborg, .dk), 
and in the center of Silkeborg. Population count about 40000.

The location matters, since these two sites are on different 60kV radials.

I have clocks at both locations, so I decided to see how well I could do 
time transfer between the two sites, only using the power line. A poor 
man's common view experiment.

http://mx15.kasperkp.dk/plcv.png


I expected it to be a lot worse. 100us is 1.8 degrees phase error, or 
10V slicer offset on 230V. Since the sense circuits are really cheap 
opto couplers, and the temperature variations on the 'city server' are 
rather extreme (parking basement), they can be responsible for an error 
at least this large.

I have a set of slightly linux specific sources that generate a shm 
refclock from the local power line and a remote observing server with a 
real refclock, if anyone wants to play with this.

/Kasper Pedersen