Radio Wave Propagation (original) (raw)
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Propagation of low-frequency radio waves
IEE Proceedings - Microwaves, Antennas and Propagation, 2000
kidio WRVCS a1 fi-cilucncics less tliiin nrotind 100 kl IZ can propagite to p i l l dislanccs with little uttenu;iticsn in llic cavity l'orincd by the earth and tlic ioiiosplicre. At tlicsc rrcqucncies, nitlily active propitgation niodcs c:in occiii' bctwan the transmillcr ancl rcceiver. Clxirigs in thc ionospheric conductivity or rcflcction height i nlluciice the relative pliascs aiid miplitudcs a[ tlic propagating inodcs :ind hence Ihcir vcctor sutn. Tlic pi-opagation is less siahlc at LF than :II VLF ; a d thc icccivcd ficld strcngth is moic difficult to predict. In this investigation, 1lic Wriveliop prograin has hccu cinplopd i n conj tunclion with previously irnpublisheci suniincr-tiinc ioiiosplieric: modcls LO cstiinalc thc rcceivcci licld strcrigth over ii iiumhcr of experimcnlal paths. The predictd viilucs havc been compared with h c Incasuretnents l o validalc the ionosphcric modcls mil the inclhod of calculation.
In earth's environment, EM waves propagate in space that not only depend on their own properties but also dictated by the environment itself. The atmosphere consists of layers of air that surround the Earth. Some of the "air" is oxygen, which we breathe, but there are also many other gasses, dust particles, and even some water vapor mixed into the air, as shown in the following figure:-As the medium between transmitting and receiving antennas play an important role, it is necessary to study the medium above the earth. It's include:-1-Structure of Troposphere:-Almost all weather phenomena take place in the troposphere. The temperature in this region decreases rapidly with altitude. Clouds form, and there may be a lot of turbulence because of variations in the temperature, pressure, and density. These conditions have a profound effect on the propagation of radio waves.
Survey of Available Experimental Data of Radio Wave Propagation for Wireless Transmission
IEEE Transactions on Antennas and Propagation, 2018
This paper provides a survey of the various experimental data available on the value of the propagation path loss of radio waves in a cellular wireless environment. It is shown starting with the Okumura et al.'s paper [1] on propagation measurements and other available published experimental data, that they all exhibit that the electric field varies as ρ-1.5 within a cellular radius of a few kilometers, where ρ is the radial distance of the receiving antenna from the transmitting one. This decay in the fields is equivalent to a propagation loss of-9 dB/octave or-30 dB for a decade of the distance. This value is independent of the nature of the ground, whether it be composed of rural, urban, suburban or water. This is the first time it is stated that the propagation path loss due to the presence of ground generates a path loss of 90 dB when the signals travel a distance of 1 km. This value is rather large when compared to a loss of 30-50 dB produced by buildings, trees and similar artifacts. Therefore, the experimental data indicate that the effect of trees, buildings and so on have a secondary influence on the decay of the electric field with distance, the dominant one is the propagation loss over an imperfect ground. Contemporary propagation models do not acknowledge this fact. Outside the cellular radius of a few kilometers the path loss appears to be 12 dB/octave or 40 dB/decade of distance. In a companion paper it will be demonstrated that the values for the path loss can be explained from an analytical standpoint without taking recourse to statistics which involves a lot of assumptions on the functional variation of the variables of interest [2].
Tropospheric Influence on Low-band Very High Frequency (VHF) Radio Waves
Asian Journal of Advanced Research and Reports
The objectives of this study are to understudy the effects of temperature and relative humidity on low-band VHF signals, obtain a propagation model for signal transmission over Calabar and to ascertain the suitability of the free space propagation model for the study terrain. Results obtained shows that temperature and relative humidity has no effect on low-band VHF signals. The suitability of the free space propagation model for the study terrain failed, as calculated results underestimated path losses in the study area. Multiple regression analysis was used to obtain a suitable propagation model for the study terrain. However, since the studied meteorological variables has no effect on low-band VHF signals in the study area, the measured path losses could be attributed to foliage, hills, distance away from the transmitter and other components of the study terrain in which the signal is propagated.
Tropospheric Influence on Ultra-High Frequency (UHF) Radio Waves
Asian Journal of Research and Reviews in Physics, 2022
This research investigates the effects of temperature and relative humidity on UHF signals. A spectrum analyzer was used in measuring UHF signals while a digital thermometer and hygrometer was used in measuring temperature and relative humidity, respectively. From results obtained, relative humidity had no significant effect on measured path loss while a positive correlation coefficient was obtained between temperature and measured path loss. This implies that an increase in temperature will lead to a decrease in received signal strength of UHF signals. Furthermore, a path loss propagation model for Calabar (P L = 37.920 + 2.796T + 0.290R +) was obtained using multiple regression analysis and we believe that the obtained result will be useful to radio engineers for UHF signal propagation in the study terrain.