IntroductionVLF (very low frequency: 3-30 kHz) waves can be generated by the natural sources (e.g., lightning discharges, energetic electrons in the magnetopshere) and by man-made VLF transmitters. The man-made VLF radiowaves are mainly used for some radio navigation services (such as RSDN-20 ("Alpha") in Russia, Omega in U.S.), time radio stations and for military communication. Due to its good penetration through the water VLF waves are used for the communication with submarines. Though during last decades the satellite signals are more actively used for the communication and navigations, the usage of VLF ground-based receivers is still actual. Since during military actions the VLF communication can be more stable than ordinary satellite communication. The VLF waves from the ground-based transmitters can be used for the study of the lithosphere structure as well. So the study of VLF radio waves propagation is an actual scientific problem.