Measurement of the field strength of radio waves in HF band

ABSTRACTMs. D. ThesisMEASUREMENT OF THE FIELD STRENGTH OF RADIO WAVES IN HF BANDN.Kubilay CEYLANFırat UniversityThe Institute of Graduate Studies in Science&EngineeringPhysics Department2007, Page: 55In this thesis, sky wave propagation in HF (High Frequency) band is analyzed and somepredictions are made for sound broadcasting.The atmosphere surrounding the Earth is divided intovarious regions according to temperature, physical activities and chemical components. Among theseregions ionosphere is of primary concern for this study and it is the region created by the solarradiation in the upper atmosphere which ionize the molecules and form positively charged ions andfree electrons. Since the quantities of positive ions and electrons are almost equal to each other,ionosphere is electrically neutral.The high frequency band, which extends from 3 to 30 MHz, is the highest frequency band thatcan be reflected back to Earth by the ionosphere plasma. It is possible to communicate with short andextensively long distances without repeaters, that?s why ionosphere is important for radiocommunication. But the change of ionosphere parameters effect HF propagation. These parameters aredensity of electrons, collisions, absorption, fading (damping), noise, refractive index, and the numberof sun spots. Because of so many parameters, an effective communication frequency arrangementshave to be made. At the international base it is performed by ITU (International TelecommunicationUnion).In this study, an ITU-compliant HF field measurement system is used in Elazığ (38.7 ºN, 39.2ºE) to measure the strength of 5.470 MHz and 7.870 MHz HF radio waves transmitted from Van-Erciş(39.03 ºN, 43.37 ºE),Kayseri (38.43 ºN, 35.30 ºE),Erzincan (39.43 ºN, 39.28 ºE), Şanlıurfa (37.07 ºN,38.46 ºE), and the diurnal and seasonal variations in signal strength are investigated.Keywords: Reflection, Refraction, Electron, Density, Propagation, Radio Waves.