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.