GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.1 - POSTER GNGTS 2023 Fig. 1. The spectrograms in LF (top) and VLF (down) recorded at Mefite INGV station are shown with the colour legend (in dB) visible at the center-left. Here are about 80 minutes for both recordings, from 1 to 30 kHz for VLF and from 30 to 96 kHz for LF. Transmitters are visible as horizontal lines where signal intensities reach some μV, and are labeled with the transmitter names. The Mefite station was programmed to sample the electrode signals from the half of November 2022 at 60 kHz, allowing the monitoring of 13 VLF transmitters, and at 192 kHz, allowing the monitoring of other 19 LF transmitters, see Fig. 1. Some of the horizontal lines were identified as harmonics of 5.25 kHz, a signal perhaps created in the PC itself. Further 5 horizontal lines in the LF band were not yet identified. The set of frequencies, locations, and power of these stations is summarized in Table 1. Table 1. VLF and LF transmitters identified in the spectrogram of the Mefite station; the power of some transmitters is unknown. Position kHz kW Position kHz kW Position kHz kW Gildeskål Nor 16.4 45 La Mour USA 25.2 250 Grindavik Isl 57.4 - Rosnay Fr 18.3 200 Bafa Tur 26.7 100 Anthorn Uk 60.0 17 Anthorn Uk 19.6 100 Negel Irs 29.7 - La Régine Fr 62.6 - Exmouth Au 19.8 1,000 Grindavik Isl 37.5 100 S. Assise Fr 63.8 - Tavolara It 20.3 50 Grimeton Sw 40.5 42.6 - Taldom-Moscov Ru 66.7 10 S. Assise Fr 20.9 50 Karlsborg Sw 44.2 - Turso Uk 68.0 - Lualualei USA 21.4 600 Niscemi It 45.9 - Baku Az 72.0 - Skelton Uk 22.1 100 Maraton Gr 49.0 250 Halifax Ca 73.6 - Rhauderfehn Ge 23.4 300 Oxford Uk 52.0 - Mainfingen Ge 77.5 50 Culter USA 24.0 1,000 Okinawa Jp 54.0 - Inskip Uk 81.0 -