For more information please read the help-information available via the help menu in the software. The following spectrograms have been recorded on july 17th 1999 with low 137kHz. There are also natural radio signals visible with the same relative strength as the Loran-C signals but they appear as curved light blue lines running diagonaly donwards. Only the south of France and the Baltic had thunderstorms and most of the activity was in the afternoon. The weak radio signals from Amateur radio transmissions in the 136kHz LF band can be completely inaudible because of the static noise caused by lightning.
Local noise shows light blue on the left side of the diagram.
A sound file can be down loaded from my site for those who would like to experiment with their own settings and compare with the G3XDV spectrogram above. Please note that the WAV file is really large and it might take a lot of time before you get it over to your computer. The total recorded time is approx. 5 minutes and 52.5 seconds g3xdv.wav . Sferics images provided by the Georg Mueller Institute.