In the present work, the analytical study for one of the modern theoretical international models which are used to predict the behavior of transferring radio waves among the transmitting/receiving stations and of affection of these waves by the atmosphere. The analytical study for the application of the REC533 international model has been made in order to reach for the conclusions that enable to forecast the frequencies that can maintain a semi-permanent reliable connection between the transmitting and receiving stations. In this study, Iraq has been adopted generally, whereas, Baghdad was taken specially to be represented as a central point. Since, the capital Baghdad has been adopted to be as a transmitting/receiving station with many stations lying within Iraqi cities and some surrounded Arabian and foreign capitals that place within the Middle East zone. Consequently, the simplified mathematical model has been proposed, which leads to predict the frequencies that can ensure the annual permanent reliable connection for different link distances and orientations.