Complex Experimental Evaluation of the Characteristics of Propagation of HF Signals Along Midlatitude Paths of Different Length and Orientation

Abstract

We outline a complex approach for measuring distance–frequency, angular, spectral, and statistical characteristics of HF signals and present the results of experimental studies of the turbidity coefficient, frequency-spread bandwidth, variations in the Doppler frequency shift, bearing, and elevation angle in a wide frequency range for the Khabarovsk–Rostov-on-Don, Moscow–Rostov-on-Don, and Cyprus–Rostov-on-Don sounding paths under various geophysical conditions. It is shown that the most probable values of the turbidity coefficient for one-hop paths in the afternoon range from 2 to 4. The turbidity coefficient decreases to about 0.6 in the twilight hours. The turbidity coefficient tends to decrease with the path length. The average frequency-spread bandwidth at the 95% level of the received signal power is found to be minimal for illuminated path and does not exceed a value from 0.1 to 0.3 Hz. The frequency-spread bandwidth increases in the sunset hours or under nonuniform illumination, but does not exceed 4 Hz. We estimated the range of Doppler frequency shift variations which are due mainly to the influence of medium-scale traveling ionospheric disturbances and do not exceed 2 Hz in the experiments. The method of one-position location of a radiation source is tested by the results of angular measurements on the basis of the IRI-2001 ionospheric model.