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In this study, the influence of the solar activity on the Maximum Usable Frequency (MUF) parameter has been achieved by adopting a monthly observed sunspots number for the years 2000 & 2010. The values of the MUF parameter has been calculated using the VOACAP international model between Baghdad city and many receiving stations which are distributed on different locations over Iraqi territory. The results of this study showed that the impact of the solar activity on the behavior of MUF parameter at year 2000 is more intense than that at the year of 2010. In the years 1920s and 1930s amateurs and professionals discovered HF communications. In the late '30s, many organizations were involved in the study of HF communications. A considerable effort was made in the U.S.A. and other countries. The Radio Propagation Unit of the U.S. Army Signal Corps provided a great deal of information and guidance on the phenomena of HF propagation in 1945. By 1948, a treatise of ionospheric radio propagation was published by the Central Radio Propagation Laboratory (CRPL) of the national Bureau of Standards. This document (NBS, Circular 462, 1948) outlined the state of the art in HF propagation. Techniques were included for: predicting the maximum usable frequencies (MUF); determining the MUF for any path at any time taking into account the various possible modes of propagation by combining theory and operational experiences; and estimating skywave field strength (1). The Maximum usable frequency (MUF) is the highest frequency at which radio waves are returned to Earth by ionospheric refraction and which can be used to transmit over a particular path under given ionospheric conditions at a specific time, the median value of MUF working 50% of the time specific time. The MUF is used to determine the frequency that provides the optimum performance for the radio communications system. The basic of the MUF represents the highest frequency by which a radio wave can propagate between given terminals by ionospheric propagation alone. The MUF in particular varies greatly throughout the day, seasonally, location of terminals, orientation, and the solar activity. The MUF is reflected from the maximum electron density within a given layer of the ionosphere, therefore the MUF must be statistically based on the electron density of ionosphere, so the frequencies higher than the MUF penetrate the ionosphere and continue into space, while frequencies lower than the MUF tend to refract in the ionosphere and return back to Earth (2).

Studying the Impact of the Solar Activity on the Maximum Usable Frequency Parameter over Iraq Territory