Measured distribution of the duration of fades in tropospheric scatter transmissions

Results of experimental measurements of fade durations at the output of tropospheric scatter receivers operating at a frequency of 950 Mc are presented. The special test equipment and the test procedures required to perform the measurements are described. The accumulated time the fades are below a reference level is shown. A family of curves representing the number of fades per hour which equal or exceed a given duration, and a family of curves representing the percentage of the total fades that equal or exceed different fade durations are presented. All the data are referenced to fade margin, which is defined as the difference between the received median level and the reference level. This enables the information given in this paper to be readily applied to other systems. A method for computing circuit reliability, based on the results of this paper, is suggested.