Diurnal and seasonal amplitude and phase variations of the radio signals of rsdn-20 transmitters and the intensity of radio noise (11.9 khz) registered in yakutsk during 2009-2017

The daily, seasonal and interannual variations of the radio noise intensity, the amplitude and phase of signals from the long-range navigation radio system RSDN-20 are analyzed based on the registration at a frequency of 11.904 kHz in Yakutsk during increase, maximum and decrease periods in the 24th solar cycle activity (2009-2017). The most pronounced seasonal daytime amplitude variations. The signal phase delay increase from day to night was recorded, which is characteristic of an increase in the effective height of the Earthionosphere waveguide. The observed phase delay decrease in the winter night time on the short radio propagation path Khabarovsk-Yakutsk can be explained by the interference of higher-order modes. There is an asymmetry of the daytime seasonal variations of the amplitude of VLF radio signals (11.904 kHz). During daytime, seasonal variations in amplitude and phase are relatively stable from year to year. Against the background of an increase in solar activity in winter, at night, the phase delay increase is recorded by 23 \pm 6^{\circ}on a shorter radio path Khabarovsk-Yakutsk (1400 km).