[time-nuts] Blackout in Europe and power line frequency jump
ik1odo at spin-it.com
Thu Nov 9 03:16:35 EST 2006
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
>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
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