The Effect of Refractivity on Propagation at UHF and VHF Frequencies

Abstract

This paper is using weather parameters to investigate the effect of refractivity on propagation in the first kilometer of the atmosphere over the English Channel for a long transhorizon path of 140 km. Different refractivity profiles are constructed based on meteorological data taken from the UK Meteorological Office in order to investigate the effects of refractivity on propagation. The analysis is made for the hourly experimental path loss between the transmitter and receiver obtained from the experimental setup comprised of two communication links. The frequency of operation of the first link is 2015 MHz and that of the second link is 240 MHz. Parabolic equation method is modelled to get an hourly modelled path loss corresponding to each hourly experimental path loss to be analyzed for the said communication links. The correlation between the modelled path loss and experimental path loss is computed for refractivity distribution recommended by the ITU and predicted profiles. It is inferred from the simulated and experimental results that little or no influence exists by the evaporation duct upon path loss at 2015 MHz specifically for a long path of 140 km over the sea.

Application of artificial neural network modeling techniques to signal strength computation

“…Long-term changes may arise when the variation of the atmospheric radio refractive index gradient is pronounced from the normal propagation values [ 4 ]. It is therefore pertinent to understand the effects of weather on radio wave propagation in order to improve the quality of radio communication signals [ 7 , 8 , 9 ]. Consequently, radio propagation models provide efficient methods of analysing and predicting the strength of these signals in this regard [ 10 ].…”

“…It has been established by several authors that radio refractivity correlates with radio signal strength [ 7 , 16 , 17 , 18 ]. By inference, the atmospheric variables (temperature, pressure, relative humidity) from which radio refractivity derives have also been found to correlate with radio signal strength and this has been reported by a number of researchers.…”

“…By inference, the atmospheric variables (temperature, pressure, relative humidity) from which radio refractivity derives have also been found to correlate with radio signal strength and this has been reported by a number of researchers. Some studies have reported the existence of correlation between RSS and atmospheric parameters of humidity and temperature [ 7 , 19 , 20 , 21 ], while others have found correlation between RSS and wind speed [ 22 , 23 , 24 , 25 , 26 ].…”

Estimation of the refractivity gradient from measured essential climate variables in Iyamho-Auchi, Edo State, South-South Region of Nigeria

“…Most essential climate variables like air temperature, relative humidity and atmospheric pressure need to be adequately accessed so as to have better local radio propagation conditions, which would enhance the quality of services of cellular network service providers, navigation and radar system designers. 277 Accordingly, accessing these essential climate variables will undoubtedly assist in providing a reliable meteorological blueprint on local radio propagation situations that will assist cellular network service providers, navigation and radar system designers in improving their quality of services [1][2][3][15][16][17][18].…”

“…These unexpected radio wave propagations could cause severe impacts to the extent of complete interruption of the communication between the transmitters and the receivers or even make radar to wholly miss its projected target. Therefore, it is essential for the to take into account the variation of the propagating radio wave resulting from the instabilities in the refractivity distribution [1][2][3][15][16][17][18]. Refractivity gradient as well as other refractivity statistics would make available some of the most needed description of the possible manifestation of refractivity related impact required for local radio wave estimation procedures [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”