G.G. Vertogradov, E.G. Vertogradova, K.G. Ershov
The experimental technique for measuring of absolute value of radio noise field intensity by spectral methods with the help of multi-frequency Doppler radar and LFM-ionosonde/direction-finder is developed. The results of measurements of radio noise field intensity are given obtained by two radiophysical methods, which were carried out in round-the-clock operation from April 2010 to August 2011 in frequency band 1500–25000 kHz. The results of statistical processing of experimental data for each month and season are grouped in 6 time intervals within the day. Statistical characteristics of radio noise are received. They are the function of distribution of fluctuations of field strength, median values of intensity of the field, standard deviations from the mean. After selection of station noise it is concluded that the difficult hypothesis of the normality of fluctuations of the radio noise level measured in decibels doesn't contradicts Kolmogorov's criterion, with a significance value of 5%. The empirical radio noise model is developed on basis of experimental data for middle-latitude propagation paths in HF wave band. It takes account of atmospheric noise due to lightning, to man-made sources. The coefficients of polynomial-logarithmic approximation of field intensity median values and standard deviations depending on frequency are given.