Based on a similar experiment at GEO, we were expecting to see the some side-bands of the 50 Hz disappear in the interruptable power source and in the magnetometers. As can be seen in spectograms of fig. 1, they do indeed disappear when we are running on battery power, but when the diesel starts there are again some sidebands. It seams that the power of the diesel is much noisier than what we get from ENEL, so it is hard to tell if the diesel somehow produces similar side-bands as ENEL, or that it is one of our own heavy machines on the interruptable power supply. Fig 2 compares the spectra when running on ENEL, battery and diesel.
