This thesis uses a method called "parabolic equation approach." This method can treat both the variations of the terrain and the refractive index simultaneously. This method makes it possible to predict the radio propagation more precisely. We can discuss the effects of the variations of the refractive index to radio signal and demo effects by using parabolic equation method. The Effective Earth Radius Factor is 4/3 suggested by CCIR so-called "Standard Atmosphere Model". But we try to find more suitable K in the Southern Taiwan area. We adopt Parabolic Equation Propagation Model to simulate real situation of radio propagation in the Southern Taiwan area and the prediction is compared with the measurement obtained previously. We can get the best K in the Southern Taiwan area is 1.8 and 1.9. The best K is greater than the value of 4/3 suggested by CCIR. Recently the government on Taiwan release more radio broadcasting licenses to the general public. As the number of radio stations increases, the interference between stations becomes more likely. There have been reports about the poor quality of broadcasting from stations. In this paper, we will study the interference using FM radio stations as an example. Given the characteristics of the transmitting antenna including location, frequency, pattern, height and power, the field strength can be computed with the equivalent earth radius factor K as a parameter. The difference in interference level is obtained under the standard atmosphere (K=4/3) and a case of K=1.55 which has been reported to be more suitable in Taiwan. Finally an extreme case that a ducting exists will be studied. Our results can be used to find more suitable separation distances free from interferences between co-channel and adjacent channel stations. By including a realistic tropospheric term, the more accurate field strength predictions can give the Spectrum Authority a better spectrum assignment tool. This has the potential to increase the number of available stations that can be made available or to reduce the interference stations may experience.

No / This paper investigates the seasonal variations of effective earth radius factor, k, in the Arabian Gulf region where non-standard propagation phenomena are commonly experienced. The k-factor is derived from the vertical profile of refractivity in the area under study. The vertical refractivity gradient, δN, in the first kilometre of the atmosphere above the ground surface is analysed using long term meteorological data. Long-term radiosonde data gathered in the United Arab Emirates (UAE), are used to calculate the variations of refractivity gradient and k-factor parameter.

Yes / A new simplified approach is proposed to evaluate the vertical refractivity profile within the lowest 1 km of atmosphere from the analysis of surface refractivity, Ns, in areas where upper air data are not available. Upper-air measurements from the nearest available radiosonde location with similar surface profile to these sites are utilized. The profiles of Ns and refractivity extrapolated to sea level, No, obtained from surface meteorological data using both fixed stations and radiosonde are investigated and compared. Vertical refractivity gradient, ΔN, is evaluated at three atmospheric layer heights within the first kilometer above the ground in addition to propagation parameters relevant to each atmospheric layer. At six sites, different approaches are compared for the analysis of three important parameters; namely effective earth radius factor, k, anomalous propagation probability parameter, β0, and point refractivity gradient at 65 m not exceeded for 1% of time, dN1. The k-factor parameter is investigated using a new weighted average approach of ΔN at 65 m, 100 m and 1 km layers above the ground. The results are compared with the latest ITU maps and tables for the same area.

The objective of this study was to provide an adequate model of the k-factor for scientific radio planning in South Africa for terrestrial propagation. An extensive literature survey played an essential role in the research and provided verification and confirmation for the novelty of the research on historical grounds. The approach of the research was initially structured around theoretical analysis of existing data, which resulted from the work of J. W. Nel. The search for analytical models was extended further to empirical studies of primary data obtained from the South African Weather Service. The methodology of the research was based on software technology, which provided new tools and opportunities to process data effectively and to visualise the results in an innovative manner by a means of digital terrain maps (DTMs) and spreadsheet graphics. MINITAB / Thesis (PhD)--University of Pretoria, 2005. / Electrical, Electronic and Computer Engineering / unrestricted