[time-nuts] Blackout in Europe and power line frequency jump

[Marco]

At 14.33 09/11/2006, Rusty wrote:

>Thanks for sending this. Those graphs were very interesting. I've certainly
>never seen a frequency deviation of that magnitude or duration before!

Same here, it has been an absolute exception.


>Your report, though, inspires me to look into more reliable and precise ways
>to measure the frequency of one's local grid. I had not actually considered
>monitoring electric fields "off the air" before, but it seems like this
>might be fairly practical.
>...
>Finally, if I may ask, I am curious why your friend monitors the 0-120Hz
>ULF/ELF frequency
>spectrum. Is the power grid the primary target of this monitoring? I don't
>know what else would be interesting in that range, but maybe there is
>something I don't know about.

Renato does a lot of research on the electromagnetic spectrum in the 
0-120 Hz band. You may have a look at his site www.vlf.it .
In this part of the spectrum there are some signals of natural 
origin, and many, many other are man-made. Often those are 
superimposed as disturbance on the 50Hz, coming from switching power 
supplies, motor controls, and any sort of industrial processes. So he 
looks at both sidebands of the 50Hz, and if a signal is "mirrored" on 
the two sides it's almost certainly not natural. The 50Hz was not the 
target of the monitoring, but it is monitored indirectly.

The 16.6Hz signal is certainly coming from the north European 
railways. Sometimes also the Russian ZEVS signals are visible around 
82 Hz - those are for communication with submarines in immersion.

Also visible are the Earth's Schuman resonances, from 7 to 50Hz. This 
is a natural resonance of the cavity made by the Earth and his 
ionosphere, excited by thunderstorms. The center frequency is near 
7.5Hz, and the harmonics are visible.  Not a real frequency standard, 
however.... :-) so sorry for the O.T. !

Marco - IK1ODO