.. it's not really precise 50Hz, just +/- 50Hz.
.. there are more than just proof of concepts, you can tell from a video, when it was made from the backround noise from the main grid.
https://www.umiacs.umd.edu/publications/seeing-enf-natural-t...
.. a few years ago, was the European electric network several minutes to late, because not every country did pay for the electric power.
https://www.nationalgeographic.com/science/article/european-...
.. it's not really precise 50Hz, just +/- 50Hz.
.. there are more than just proof of concepts, you can tell from a video, when it was made from the backround noise from the main grid.
https://www.umiacs.umd.edu/publications/seeing-enf-natural-t...
.. a few years ago, was the European electric network several minutes to late, because not every country did pay for the electric power.
https://www.nationalgeographic.com/science/article/european-...