A.P. Kamantsev - Post-graduate Student, Kotelnikov IRE RAS. E-mail: kama@cplire.ru E.T. Dilmieva - Post-graduate Student, Bauman MSTU A.V. Mashirov - Trainee Researcher, Kotelnikov IRE RAS V.V. Koledov - Dr.Sc. (Phys.-Math.), Leading Researcher, Kotelnikov IRE RAS