Effective earth radius variation and diffraction fading on terrestrial path

Effective earth radius factor (k factor) is an important parameter for the assessment of clear-air propagation on terrestrial paths. Its variation obtained from the measurement of vertical distribution of atmospheric refractivity is studied in the paper. Two year statistics of the k factor are given for the whole year and different months. The related clear-air propagation impairment on the 10 GHz terrestrial path is shown in the example. A typical diffraction fading event is analyzed by a comparison of measured time evolution of received signal level and of a simulated one using measured refractivity. A direct correspondence between the time evolution of the effective earth radius factor and of attenuation due to reduced path clearance is so demonstrated.