University of Ghana http://ugspace.ug.edu.gh UNIVERSITY OF GHANA COLLEGE OF BASIC AND APPLIED SCIENCES DEVELOPING AND VALIDATING OF PREDICTIVE MODEL FOR RADIOFREQUENCY RADIATION EMISSION WITHIN THE VICINITY OF FM STATIONS IN GHANA. BY Kingsley Ahenkora-Duodu (10507023) THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF MASTER OF PHILOSOPHY (MPHIL) RADIATION PROTECTION DEGREE. DEPARTMENT OF NUCLEAR SAFETY AND SECURITY, SCHOOL OF NUCLEAR AND APPLIED SCIENCE. JULY 2016. University of Ghana http://ugspace.ug.edu.gh DECLARATION This thesis is the result of research work undertaken by Kingsley Ahenkora-Duodu towards an award of the MPhil Radiation Protection in the Department of Nuclear Safety and Security of the School of Nuclear and Allied Sciences, University of Ghana, under the supervision of Dr. Joseph Kwabena Amoako and Prof. Emmanuel Ofori Darko. Signed……………………………. Date…………………………………… Kingsley Ahenkora-Duodu (Student) Signed……………………………. Date…………………………………… Dr. Joseph Kwabena Amoako (Principal Supervisor) Signed……………………………. Date…………………………………… Prof. Emmanuel Ofori Darko (Co-Supervisor) i University of Ghana http://ugspace.ug.edu.gh ABSTRACT The rapid growing number of FM stations with their corresponding antennas have led to an increase in the concern of the potential health risks that may arise as a result of exposure to RF radiations. The main objective of this research was to develop and validate a predictive model with real time measured data for FM antennas in Ghana. Theoretical and experimental assessment of radiofrequency emission due to FM antennas has been analysed. The maximum and minimum electric field spatial average recorded was 7.17E-01 ± 6.97E- 01V/m at Kasapa FM and 6.39E-02 ± 5.39E-02V/m at Asempa FM respectively. At a transmission frequency range of 88 -108 MHz, the average power density of the real time measured data ranged between 3.92E-05W/m2 and 1.37E-03W/m2 whiles that of the FM model varied from 9.72E-03W/m2 to 5.35E-01W/m2 respectively. Results obtained showed a variation between measured power density levels and the FM model. The FM model overestimates the power density levels as compared to that of the measured data. The impact predictions were based on the maximum values estimated by the FM model, hence these results validates the credibility of the impact analysis for the FM stations. The general public exposure quotient ranged between 9.00E-03 and 2.68E-01 whilst that of the occupational exposure quotient varied from 9.72E-04 to 5.35E-02. The results obtained were found to be in compliance with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) RF exposure limit. ii University of Ghana http://ugspace.ug.edu.gh DEDICATION I dedicate this thesis work to the Lord God Almighty for His divine grace, favour, guidance and protection throughout this period, also to my lovely parents Mr and Mrs Ahenkora- Duodu, my siblings; Emmanuel Ahenkorah, Francis Akwaboah, Kwame Anokye, Lydia, Mercy, Charity, Deborah and the entire Ahenkorah family and all well-wishers. iii University of Ghana http://ugspace.ug.edu.gh ACKNOWLEDGMENTS I wish to express my sincerest appreciation to my supervisors, Dr. Joseph Kwabena Amoako and Prof. Emmanuel Ofori Darko for their expert supervision, guidance, patience and encouragement. My profound gratitude to the management of Radiation Protection Institute (RPI) of the Ghana Atomic Energy Commission (GAEC) for providing the available measuring instruments and its accessories for the research. My sincere thanks also go to the entire staff of Radiation Protection Institute (RPI) of the Ghana Atomic Energy Commission (GAEC), especially Mr. Collins Kafui Azah and Mr. Samuel Osei, for their support and assistance. I am also grateful to the management of the National Communication Authority (NCA), Star FM, Vision One FM, the Head of department of Nuclear Safety and Security of Graduate School of Nuclear and Allied Sciences, Justice Appiah of NCA, Battels Haizel of Star FM and all others who assisted me in devise ways. I am most grateful to Prof. E. O. Darko (Director, Radiation Protection Institute) and Dr. J. K. Amoako (Deputy Director, Radiation Protection Institute) for allowing me unrestricted access to the Institute’s laboratories and facilities. Am also grateful to all my colleagues, Peter Osei, Joshua Kalognia, Selasie, Capacity, Sadiq, Patience, Alberta, Lilian and Veronica for your support and constructive criticisms. Finally, I acknowledge Mr. Tetteh Quarshie of RPI and my brother WO II Emmanuel Ahenkorah of the Ghana Air Force for their support and assistance during the field work. iv University of Ghana http://ugspace.ug.edu.gh TABLE OF CONTENTS DECLARATION ............................................................................................................ i ABSTRACT ................................................................................................................... ii DEDICATION .............................................................................................................. iii ACKNOWLEDGMENTS ............................................................................................ iv TABLE OF CONTENTS ............................................................................................... v LIST OF TABLES ......................................................................................................... x LIST OF FIGURES ..................................................................................................... xii ABBREVIATIONS .................................................................................................... xvi CHAPTER 1 .................................................................................................................. 1 INTRODUCTION ......................................................................................................... 1 1.1 Background ..................................................................................................... 1 1.2 Statement of the problem ................................................................................ 4 1.3 Objectives ........................................................................................................ 5 1.4 Relevance and Justification of the work ......................................................... 6 1.5 Scope and Limitation ...................................................................................... 7 1.6 Structure .......................................................................................................... 7 CHAPTER TWO ........................................................................................................... 8 LITERATURE REVIEW .............................................................................................. 8 2.1 Introduction ..................................................................................................... 8 v University of Ghana http://ugspace.ug.edu.gh 2.2 Allocation of Frequency in Ghana .................................................................. 9 2.3 Quantities and units ......................................................................................... 9 2.3.1 Dosimetric quantities ............................................................................. 10 2.4 Measurement Parameters .............................................................................. 11 2.4.1 Frequency range ..................................................................................... 11 2.4.2 Source Parameters .................................................................................. 12 2.5 Exposure categories....................................................................................... 18 2.5.1 Occupational exposure ........................................................................... 18 2.5.2 Public exposure ...................................................................................... 19 2.6 Standard for limiting exposure to EM fields ................................................. 19 2.6.1 Guidelines of the International Commission for Non-Ionizing Protection (ICNIRP) .............................................................................................................. 19 2.6.2 Standard of the Institute for Electrical and Electronic Engineers .......... 20 (IEEE) - 3 kHz to 300GHz ................................................................................... 20 2.6.3 FCC Exposure Guidelines...................................................................... 21 2.7 Exposure Measurements ............................................................................... 23 2.7.1 Exposure zone ........................................................................................ 23 2.7.2 Site Measurement Analysis.................................................................... 24 2.7.3 Broadband measurement ........................................................................ 24 2.7.4 Narrowband Measurements ................................................................... 25 2.7.5 Calibration requirements ........................................................................ 26 2.8 Numerical models and Theoretical Estimations Methods ............................. 27 2.8.1 Friis free space ....................................................................................... 28 2.8.2 The point source model .......................................................................... 28 2.8.3 Ray tracing ............................................................................................. 29 2.8.4 Two Ray model ...................................................................................... 29 2.8.5 Finite-difference time-domain method (FDTD) .................................... 32 2.8.6 Multiple-Region Finite-difference time-domain method (MR/FDTD) . 32 2.8.7 Methods of moment (MOM) ................................................................. 33 vi University of Ghana http://ugspace.ug.edu.gh 2.8.8 FDTD/ray tracing ................................................................................... 33 2.9 Practical problems using Numerical Models and Theoretical Estimations... 33 2.10 Advantages of Numerical Models and Theoretical Estimations ................... 34 2.11 Limitations of Numerical Models and Theoretical Estimations ................... 34 2.12 Assessment of Radiofrequency Exposure using numerical model and theoretical estimation methods. .................................................................................................. 35 2.13 Assessment of Radiofrequency Radiation within the Vicinity of Some GSM Base Stations in Ghana. ............................................................................................ 36 2.14 Review of Studies on Assessment of the Levels of Radiofrequency Fields in the Vicinity of FM Radio Stations in Accra, Ghana. ..................................................... 37 2.15 Review of Comparative Studies Between the ITU-T Prediction Model For Radiofrequency Radiation Emission and Real Time Measurements at Some Selected Mobile Phone Base Stations in Accra, Ghana.......................................................... 38 2.16 An Engineering Assessment of the Potential Impact of Federal Radiation Protection Guidance on the AM, FM, and TV Broadcast Services. ........................ 38 2.17 Review of studies on Occupational Exposure ............................................... 40 2.17.1 Cancer .................................................................................................... 40 2.17.2 Other outcomes ...................................................................................... 41 CHAPTER THREE ..................................................................................................... 43 MATERIALS AND METHODS ................................................................................. 43 3.1 Introduction ................................................................................................... 43 3.2 Sampling ....................................................................................................... 43 3.3 Measurement instrumentation ................................................................... 44 vii University of Ghana http://ugspace.ug.edu.gh 3.3.1 Anritsu Spectrum Analyser .................................................................... 44 3.3.2 Bi-conical Element................................................................................. 44 3.3.3 Garmin Oregon 200 GPS ....................................................................... 44 3.4 Methodology ................................................................................................ 46 3.4.1 Measurement set-up............................................................................. 46 3.4.2 Measurement of coordinates .................................................................. 46 3.4.3 Determination and Documentation of the Test point(s) ........................ 47 3.4.4 Measurement of electric field .............................................................. 48 3.4.5 Determination of field strength........................................................... 49 3.5 Electric field Spatial Average ..................................................................... 51 3.6 Uncertainty Estimation. .............................................................................. 52 3.7 Numerical Prediction Model. ..................................................................... 53 3.8 Sample Calculation ....................................................................................... 58 3.8.1 Power Density for the Numerical Predictive Model ............................... 58 3.8.2 Real time measured power density ........................................................ 59 3.8.3 Electric field Spatial Average .................................................................. 60 3.8.4 Exposure Quotient ................................................................................. 60 3.8.5 Uncertainty Estimation .................................................................................. 61 CHAPTER FOUR ........................................................................................................ 63 RESULTS AND DISCUSSION .................................................................................. 63 4.1 Introduction ................................................................................................... 63 4.2 FM radiating antennas Power density levels ................................................. 63 4.2.1 Measured Power Density Levels ........................................................... 64 4.2.2 The Predictive model power density levels ........................................... 66 4.3 FM model verification ................................................................................... 69 4.4 Limitations of the model ............................................................................... 71 viii University of Ghana http://ugspace.ug.edu.gh 4.5 Electric field spatial average ......................................................................... 72 4.6 Exposure quotient .......................................................................................... 73 4.7 Comparison with International Standards ..................................................... 75 4.8 Comparison of results with other researched works. .................................... 75 CHAPTER FIVE ......................................................................................................... 77 CONCLUSIONS AND RECOMMENDATIONS ...................................................... 77 5.1 Conclusions ................................................................................................... 77 5.2 Recommendations ......................................................................................... 78 5.2.1 Recommendation to National Communication Authority (NCA). ........ 78 5.2.2 Recommendation to FM radio stations .................................................. 78 5.2.3 Recommendation to Occupationally Exposed Workers ........................ 79 5.2.4 Recommendation to the General Public ................................................ 79 5.2.5 Recommendation for Further Studies .................................................... 79 REFERENCE ............................................................................................................... 81 APPENDICES ............................................................................................................. 86 APPENDIX A: EM FIELDS EXPOSURE REFERENCE LEVELS ...................... 86 APENDIX B: MEASUREMENTS TABLES .......................................................... 94 APENDIX C TECHNICAL PARAMETERS FOR THE FM ANTENNAS ..... 111 APPENDIX D COMPARATIVE GRAPHS FOR MEASURED AND CALCULATED POWER DENSITY LEVELS OF FM STATIONS ................... 112 APPENDIX E SSPECTRUM ANALYZER DATA ........................................... 117 ix University of Ghana http://ugspace.ug.edu.gh LIST OF TABLES 4.1 Maximum and Minimum Power density values of surveyed……………....64 4.2 Maximum and Minimum Power density values (Numerical Predictive)…..66 Appendix Table Page A1 IEEE MPE for occupational exposure (IEEE, 2006)……………..…………85 A2 IEEE MPE for general public (IEEE, 2006)………………………...……….86 A3 IEEE MPE action levels from the main telecommunication …………….......87 A4 FCC Limits for MPE for General Public (FCC, 1997)……………………....87 A5 FCC Limits for MPE for Occupational (FCC, 1997)………………………...88 A6 ICNIRP reference levels (unperturbed rms values) (ICNIRP, 1998)…….......89 A7 ICNIRP reference levels for general public exposure from the main telecommunications services and systems (WHO)………...………………...90 A8 Typical sources of electromagnetic fields (Miller, 2002)………..…………..91 A9 Examples of emissions in the frequency band from 9 kHz TO 300 GHz (ECC, 2004)………………………………………………………………….91 A10 Some quantities and SI-units used in the radiofrequency band (ICNIRP, 2009)..……………………………………………………………92 x University of Ghana http://ugspace.ug.edu.gh B1 Electric field spatial average strength Measured Power density levels (W/m2) surveyed for various mobile base stations .......................................................93 B2 Measured Power density levels (W/m2) of the various FM antennas……....101 B3 FM model Power density levels (W/m2) of the various FM antennas ……………………………………………………………..……………....109 xi University of Ghana http://ugspace.ug.edu.gh LIST OF FIGURES 2.1 Electromagnetic Wave (FCC, 1997)………………..…………………….9 2.2 Electromagnetic spectrum (FCC, 1997)………………….…………………10 2.3 Capacitor microphone FM generator (Miller, 1999)……………..…………13 2.4 Field regions around an EM source…………………………………………15 2.5 Near and Far-Field Nomenclature (ICNIRP, 2009)…………………………16 2.6 Exposure zones……………………………………………………………...23 2.7 Sample configurations for calculating exposure at ground level (ITU K52)..29 2.8 Sample configurations for calculating exposure at an adjacent building…….30 2.9 Sample of calculated and measured power densities (free-space equivalent) for an actual FM station (Gailey & Tell, 1985)………………………………38 3.1 Anritsu Spectrum Master MS2721B with PC ……………………………….42 3.2 Location of FM antennas using the ArcGIS software …………………….....44 3.3 Shows the coordinates and test points of Asempa FM radiating antenna using the ArcGIS software …..……………………………………………………...….46 3.4 Spectrums for Location ‘A2’ of Marahaba 99.3MHz FM …………...……....49 3.5 Schematic diagram for calculating exposure at ground level…….…………..54 4.1 4.1 Plot of power density against distance for Marahaba FM (real time measurement)………………………………..………………………………...63 xii University of Ghana http://ugspace.ug.edu.gh 4.2 4.2 Plot of power density against distance for Marahaba FM (Numerical Predictive Model)…………………………….……..………………………..68 4.3 Predictive model and real-time measured power densities of an actual FM station……………………………….…………………...…………………...69 4.4 Spatial average electric field strength of each FM station ………………......72 xiii University of Ghana http://ugspace.ug.edu.gh Appendix Figure E2 Spectrum location ‘B2’ for Marahaba 99.3MHz FM station…………...…..116 E3 Spectrum location ‘C2’ for Marahaba 99.3MHz FM ………………………116 E4 Spectrum location ‘D2’ for Marahaba 99.3MHz FM ………………………117 E5 Spectrum location ‘E2’ for Marahaba 99.3MHz FM ………………...…….117 E6 Spectrum location ‘F2’ for Marahaba 99.3MHz FM ………...……..……...118 E7 Spectrum location ‘G2’ for Marahaba 99.3MHz FM ………………………118 E8 Spectrum location ‘H2’ for Marahaba 99.3MHz FM ………………………119 E9 Spectrum location ‘I2’ for Marahaba 99.3MHz FM………………………...119 E10 Spectrum location ‘J2’ for Marahaba 99.3MHz FM………………...……...120 E11 Spectrum location ‘K2’ for Marahaba 99.3MHz FM…………...…………..120 E12 Spectrum location ‘L2’ for Marahaba 99.3MHz FM………………………..121 xiv University of Ghana http://ugspace.ug.edu.gh List of Plate 3.1 Spectrum Analyser in use with bi-conical element (Star 103.5MHz FM)…...47 3.2 A typical FM radiating antenna (Marahaba 99.3MHz FM)………………….48 xv University of Ghana http://ugspace.ug.edu.gh ABBREVIATIONS Acronym: ANSI American National Standard Institute EIRP Effective Isotropic Radiated Power EMF Electromagnetic fields ECC Electronic Communications Committee FCC Federal Communications Commission FM Frequency Modulation GAEC Ghana Atomic Energy Commission GHz Giga Hertz ICNIRP International Commission on Non-Ionizing Radiation Protection IEEE Institute for Electrical and Electromagnetic Engineers ITU International Telecommunication Union NCA National Communication Authority NCRP National Commission for Radiation Protection NIR Non Ionizing Radiations NRA Nuclear Regulatory Authority xvi University of Ghana http://ugspace.ug.edu.gh MBS Mobile phone Base Station MHz Mega Hertz MRI Magnetic resonance imaging MPE Maximum Permissible Exposure PCS Personal Computer Systems RF Radio frequency SAR Specific Absorption Rate UHF Ultra high frequency VHF Very high frequency VDU Video display unit WHO World Health Organisation Units: Hz Hertz 1Hz = 1 cycle per second. MHz Megahertz. 1MHz = 1000000 cycle per second. GHz Gigahertz. 1GHz = 1000000000 cycle per second. V.m-1 Volts per meter: The unit of measurement of electric field xvii University of Ghana http://ugspace.ug.edu.gh W.m-2 Watt per square meter: The unit of measurement of power density Definitions: Epidemiology The science that studies the patterns, causes and effects of health and disease conditions in defined populations. Exposure Quotient The ratio of the measured levels to Limits for Maximum Permissible Exposure (MPE) levels by ICNIRP. Extremely Low Frequency The frequency range from 3 Hz to 3000 Hz. Maximum Permissible Exposure An exposure limit or guideline for RF energy exposure published by a recognized consensus standards organization, such as the IEEE Radio Frequency The frequency range from 3 kHz to 300 GHz. xviii University of Ghana http://ugspace.ug.edu.gh CHAPTER 1 INTRODUCTION 1.1 Background Radio frequency (RF) energy is another name for radio waves. It is one form of electromagnetic energy that makes up the electromagnetic spectrum. Electromagnetic energy (or electromagnetic radiation) consists of waves of electric and magnetic energy in motion (radiating) through space. The region where the waves are found is known as electromagnetic field. High frequency electromagnetic fields are defined in terms of the electric field strength E and magnetic field strengths H (ICNIRP, 2009) Radio waves are created due to the motion of electrical charges in the antennas. As they are developed, these waves radiate far from the antenna. The radio signals are conveyed from the modified antennas. The space around a source antenna is often divided into two zones: the near-field zone and the far-field zone. The near-field zone can be further divided into two regions: the reactive near-field region and the radiating near-field region. The region of space immediately surrounding the antenna in which the induction (reactive) field exists is known as the reactive near-field region. The antennas are created to transmit majority of the signal away horizontally, or just below the horizontal, instead of at steep angles toward the ground. All electromagnetic waves travel at the speed of light. The main differences between the other types of waves are the distances covered by one cycle of the wave and the number of waves that pass a certain point during a set time period. The wavelength can be defined as the distance covered by one cycle of a wave and the frequency is the number of waves passing a particular point in a second. For any form of an electromagnetic wave, the 1 University of Ghana http://ugspace.ug.edu.gh wavelength multiplied by the frequency gives the speed of light. The frequency of an RF signal is in units called hertz (Hz). RF energy includes waves with frequencies varying from 3 kHz to 300 GHz. Modulation is a means of sending signals of low frequency over long distances without a huge loss of energy by the use of another wave of very high frequency known as a carrier wave. High frequency signals are more directional and less diffracted because high frequency wave possess smaller wavelength. Also smaller antennas are required because the size of the antenna has to be of the same sort of size as that of the wavelength of the signal to be transmitted. The basic methods of modulation are; frequency modulation (FM), phase modulation (PM) and amplitude modulation (AM). FM is a method of broadcasting electrical signals that cannot travel very far on its own. During this process, the signal is imposed or 'imprinted' on a carrier wave whose frequency increases or diminishes with the frequency of the signal. FM is normally used in these five major categories; Noncommercial broadcasting at 88 – 90MHz, Commercial broadcasting at the frequency of 200kHz channel bandwidths within 90 to 108MHz, Television audio signals with 50kHz channel bandwidths at 54 to 88kHz, Narrowband public service channels from 108 to 174MHz and Narrowband amateur radio channels at 29.6MHz, within 52 to 53MHz, 144 to 147.99MHz, 440 to 450MHz and in the excess of 902MHz. The output powers range from milliwatts level for amateur up to 100kW for broadcast FM. Antennas used for FM radio broadcast stations normally consist of an array of elements stacked vertically and typically side-mounted on a tower. The elements are usually spaced about one wavelength apart and are fed in phase with power distributed equally among the elements (FCC, 97). The limited range for FM transmission is due to the earth’s curvature. Standard broadcast FM uses a 200 kHz bandwidth for each station. 2 University of Ghana http://ugspace.ug.edu.gh The maximum allowed deviation around the carrier is ±75kHz and 25 kHz guard band at the upper and lower ends are also provided (Miller, 1999). Electromagnetic radiation can be categorized into two types: ionizing radiation and non-ionizing radiation. All radiation that has enough energy to move atoms in a molecule around or cause them to vibrate or pump an electron to a higher energy state, but does not possess enough energy to remove electrons, is termed as non- ionizing radiation. The energy levels associated with RF and microwave radiation, are not higher enough to cause the ionization of atoms and molecules, and RF energy is a typical example of non-ionizing radiation. Other forms of non-ionizing radiation include visible light, infrared radiation, and other types of electromagnetic radiation with relatively low frequencies One of the most relevant use of RF energy is for telecommunications. TV and Radio broadcasting, cordless phones, wireless phones, pagers, police and fire department radios, point-to-point links, and the satellite communications all depend on RF energy. Other uses of RF energy include microwave ovens, industrial heaters and sealers, radar, and medical treatments. RF energy, especially at microwave frequencies, can heat water. Since most food has high water content, microwaves can cook food quickly. Radar also make use of RF energy to track cars and airplanes. Industrial heaters and sealers use RF energy to mold plastic materials, glue wood products, seal leather items such as shoes and pocketbooks, and process food. Medical uses of RF energy include pacemaker monitoring and programming (ICNIRP, 2009). One clear effect of exposures to high levels of RF radiation is heating of exposed tissues. The body has effective ways to regulate its temperature, but if exposures are too intense the body no longer copes. 3 University of Ghana http://ugspace.ug.edu.gh Exposure guidelines with reference to the field strength, power density and localized SAR were then obtained from this threshold value. In addition, the FCC, ITU, NCRP, IEEE, and ICNIRP guidelines vary depending on the frequency of the RF exposure. This is due to the finding that whole-body human absorption of RF energy varies with the frequency of the RF signal. The most restrictive limits on whole-body exposure are in the frequency range of 30-300 MHz where the human body absorbs RF energy most efficiently (ICNIRP, 2009). 1.2 Statement of the problem It has been known for some time that high intensities of RF radiation can be harmful due to the capacity of RF energy to heat biological tissue rapidly. Radio broadcast station transmit their signals via RF radiation. As at the first quarter of 2010, there were approximate 216 radio stations on the air nationwide (Azar, 2013). The number has increased significantly to the current approximation of 390 radio stations in Ghana as at the first quarter of 2015. Out of this number, 309 stations are in operation currently. Thirty seven (37) public radio station, Sixty three (63) community radio stations, Seventeen (17) campus radio stations and 273 commercial radio stations. Out of this number about 47 FM stations are authorised in the Greater Accra Region with 46 in operation. FM broadcast stations in Ghana transmit at RF frequencies between 88 to 108MHz. The growing number of FM broadcast stations in Ghana calls for concern to potential hazards which could exist with respect to a given transmission. Moreover most of these FM broadcast antennas are located in residential areas of which members of the general public as well as workers could be exposed unknowingly. 4 University of Ghana http://ugspace.ug.edu.gh Studies done so far on the exposure assessments due to FM stations installations was based on data from real time measurements. Analytical and numerical models could be used to predict the power density from an electromagnetic radiator. Numerical prediction models are useful in estimating the levels of the field strengths in a certain exposure situation in order to determine if measurements are needed and what equipment would be appropriate. Analytical and numerical prediction models can also be used to complement measurements made to verify that the results from the measurements do correspond. In order to address this problem there is the need to expand the scope of research in radiofrequency fields of FM broadcast antennas in Ghana. The Federal Communications Commission (FCC), the U.S. Environmental Protection Agency (EPA), International Telecommunication Union (ITU) and other organizations have proposed analytical and numerical prediction models that can predict electromagnetic field strength and power density from a radiating radiofrequency source. Most of these models predict values which may vary significantly from the real time measurements. It is therefore necessary to work to ensure that analytical and numerical estimated values are very close to that of real time measurements made. The proposed research seeks to develop and validate a predictive model with real time measured data in assessing the levels of radiofrequency fields within the vicinity of FM broadcasting antennas in Ghana. 1.3 Objectives The primary objective of this study is to develop and validate a predictive model with real time measured data. The specific objectives of this research work are to: 5 University of Ghana http://ugspace.ug.edu.gh  To determine the levels of RF fields from FM radiating antennas using real time measurements.  To determine the levels of RF fields from FM radiating antennas using the predictive model.  To compare the estimated levels of exposure to the limits set by International Commission on Non-Ionizing Radiation Protection (ICNIRP) whose limits have also been adopted by the Radiation Protection Institute (RPI) in Ghana and international standards and organisations such as FCC, IEEE and WHO. 1.4 Relevance and Justification of the work The rapid growing number of FM stations with their corresponding antennas have led to an increase in the concern of the potential health risks that may exist to occupationally exposed workers as well as the general public. In spite of these concerns, there is very little known about the level of exposure to RF radiation from FM broadcasting antennas. Geographical factors, location, cost of equipment and limited human resource makes it difficult to assess radiofrequency exposure from the numerous FM radiating antennae sprung across nationwide. These factors calls for the use of analytical and numerical models which can be used to assess radiofrequency exposure from FM radiating antennas. After the completion of this research, it will be easy and cost effective to estimate the level of radiofrequency radiation exposure from FM broadcasting antennas using numerical predictive model. The results may also provide policy makers in Ghana, the needed information to define national policies and monitoring of site and procedures of FM radiating antennas and others in the country. 6 University of Ghana http://ugspace.ug.edu.gh 1.5 Scope and Limitation Ten (10) operational FM broadcast antennae have been covered for the validation of the predictive model. All the studios of the FM stations were located in the Greater Accra region. Eight (8) radiating antennas out of the ten were located in the Eastern region of Ghana whiles two (2) of the antennas were located in Greater Accra. Measurements would be made twelve (12) times in each of the ten (10) FM radiating antennas at a transmission peak period during the day. FM radiating antennas located around schools, hospitals and other residential places will be used due to the high population of people at such places. 1.6 Structure The research work has been structured as follows; in chapter one, introductory notes on electromagnetic waves and radiofrequency fields with emphasis on their application in communication and in the industries. Chapter two reviews literatures related to the thesis topic to justify this work. Chapter three elaborates the equipment and procedures used in the data collection. In chapter four, the data obtained from the study is analysed and presented in the form of tables and or in figures. Chapter five draws the conclusions from the research work and also made recommendations to appropriate organisations and for further studies based on the results of this study. 7 University of Ghana http://ugspace.ug.edu.gh CHAPTER TWO LITERATURE REVIEW 2.1 Introduction Radio transmission is relatively a very new technology, which started in the theoretical work of Maxwell and experimental work of Hertz, a German physicist. Many others have also made contributions, including the development of devices which could detect the presence of radio waves (Aslan, 1972). Over the years, the transmission of radio waves has become an established technology which is taken for granted and which among other things provides for broadcasting to our homes for entertainment, the most recent development resulting in the domestic satellite dish antenna (Kitchen, 2001). Electromagnetic fields (EMFs) cover over large fields when generated for communication, broadcasting and radar devices, but generally spreads only over small areas when used in industrial, medical and consumer devices. (Health Canada, 2009). Prior to World War II, hazard assessment of NIR received little or no attention from governments and authorities charged with developing safety practices for operations involving radiations (Cember and Johnson, 2009). Institutions and telecommunication organisations such as the Federal Communications Commission (FCC), International Telecommunication Union (ITU), and European Health Risk Assessment Network on Electromagnetic Fields Exposure (EHRAN) have furnished and provided recommendations and guidelines with the aim of protecting the general public and workers from the harmful effects of both ionizing and non-ionizing radiations. Other renowned institutions includes; National Council on Radiation Protection and Measurements (NCRP), the International Commission on 8 University of Ghana http://ugspace.ug.edu.gh Non-Ionizing Radiation Protection (ICNIRP), the World Health Organisation (WHO) and the International Radiation Protection Association (IRPA). 2.2 Allocation of Frequency in Ghana The National Communication Authority (NCA) is the central regulatory body in charge with the assigning, regulating and allocating the usage of frequencies in Ghana. Allocation of frequencies includes those used in navigation, marine, mobile communication, broadcasting and associated purposes. The NCA ensures that all these operations are operating in compliance with national and international standards. The main objective of NCA is to regulate the provision of communication services in Ghana. Mobile phone base stations in Ghana transmit at a frequency of 900MHz for voice communication and 1800MHz for data communications. FM stations operate within the frequency band of 88 – 108 MHz whiles the television (TV) broadcasting stations transmit within the UHF and VHF band. Mobile phone base stations also transmit at a frequency of 900MHz for voice communication and 1800MHz for data communications. 2.3 Quantities and units RF fields are quantified in terms of electric field strength E and magnetic field strength H (ICNIRP, 2009). For radiation protection purposes dosimetric quantities are defined to describe sources and field properties and to quantify the exposure of the human body to RF radiations. Figure 2.2 shows the electromagnetic spectrum. Fig 2.1 Electromagnetic Wave ( FCC, 1997) 9 University of Ghana http://ugspace.ug.edu.gh A dosimetric quantity widely adopted to estimate the absorbed energy and its distribution is the specific absorption rate (SAR), defined as the time derivative of the Fig 2.2 Electromagnetic spectrum (FCC, 1997) incremental energy, dW, absorbed by or dissipated in an incremental mass, dm, contained in a volume element, dV, of a given density ρ (ICNIRP, 2009). d dW  d dW  SAR = = -------------------------------------------- (2.1) dt dm dt dV  Unit of SAR is watt per kilogram (W.kg-1). 2.3.1 Dosimetric quantities ICNIRP recognizes that the entity of a given effect of RF exposure is related not only to the level of the external field, but also to the coupling of the field with the exposed body, or selected organs (ICNIRP, 1998). The effects, therefore, are better described by quantities that reflect the efficiency by which the external exposure causes a certain biological effect. These are termed biological effective quantities or dosimetric quantities. Many dosimetric quantities have been identified as appropriate for different interaction mechanisms and biological effects. Generally these quantities cannot be directly measured because they are internal to the body. 10 University of Ghana http://ugspace.ug.edu.gh 2.4 Measurement Parameters 2.4.1 Frequency range 2.4.1.1 3 kHz to 300 MHz Services in this frequency range include maritime navigational communications, aeronautical radio-navigation and radio communication, analogue AM radio broadcasting, shortwave broadcasting, land mobile communication and fixed services, VHF radio (FM) and television broadcasting and amateur radio communication. Health Canada maintains that measurement procedures and techniques over this frequency range vary according to the frequency and the type of service (Health Canada, 2009). In general, for services below 300 MHz, measurements of both the electric and the magnetic fields may be required. In addition, in cases of some high- power transmissions (e.g. AM radio service) measurements of induced current and contact current may also be required. 2.4.1.2 300 MHz to 300 GHz Services operating in this frequency band include ultra-high frequency (UHF) television and digital radio broadcasting, fixed, land mobile/personal computer systems (PCS) and satellite systems. Over this frequency range, the wavelengths of the electromagnetic fields and the dimensions of the antenna are relatively short, measurement locations are usually situated in the far field region, and in general, only electric (E) field measurements are required. In the far field region, the magnetic (H) field and the electric (E) field are related by a constant. In this case, measuring only the |E|2 component can approximate the power density (Health Canada, 2009). 11 University of Ghana http://ugspace.ug.edu.gh 2.4.2 Source Parameters RF electromagnetic sources radiate energy into space via antennas installed on towers and buildings. These sources have widely different characteristics and thus require proper selection of instrumentation in hazard determination. Below are the pertinent characteristics of these sources. 2.4.2.1 Modulation The frequency of the human voice ranges from about 20 to 3000Hz. If these frequencies are transmitted directly as radio waves, interference would cause them all to be ineffective. Another limitation of equal importance is the virtual impossibility of transmitting such low frequencies since the required antennas for efficient propagation would be kilometres in length. The solution is modulation, which allows propagation of the low-frequency intelligence with a high-frequency carrier. Basic to the field of communication is the concept of modulation. Transmitted electromagnetic waves may have various forms. The most fundamental form is a continuous wave (CW) or un-modulated carrier in which the wave oscillates at a single frequency as shown in equation (2.2). Such carriers may be modulated by another signal or message. V V sin(t ) ................................................ (2.2) p Where v = instantaneous value Vp = peak value ῳ= angular velocity = 2πf 12 University of Ghana http://ugspace.ug.edu.gh Φ = phase angle If the amplitude term, Vp, is the parameter varied, it is called amplitude modulation (AM).If the frequency is varied, it is frequency modulation (FM). Varying the phase angle, Φ, results in phase modulation (PM). FM is superimposing the intelligence signal on a high-frequency carrier’s frequency departs from its reference value by an amount proportional to the intelligence amplitude. Figure 2.3 Capacitor microphone FM generator (Miller, 1999). Fig.2.3 is a very simple, yet highly instructive, FM transmitting system. It consists of an LC tank circuit, which, in conjunction with an oscillator circuit, generates a sine- wave output. The capacitance section of the LC tank is a capacitor microphone. This popular type of microphone often referred to as a condenser mike and is in fact a variable capacitor. When no sound waves reach its plates, it presents a constant value of capacitance at its two output terminals. However, when sound waves reach the mike, they alternately cause its plates to move in and out. This causes its capacitor to go up and down around its centre value. The rate of this capacitor change is equal to 13 University of Ghana http://ugspace.ug.edu.gh the frequency of the sound waves striking the mike, and the amount of capacitance change is proportional to the amplitude of the sound waves (Miller, 1999). 2.4.2.2 Near Field and Far Field Regions The space around a radiating antenna can be divided fundamentally into two regions namely, the near field and the far field region. The near-field zone can be further divided into two regions: the reactive near-field region and the radiating near-field region (HPB, 1999). The region of space immediately surrounding the antenna in which the induction (reactive) field exists is known as the reactive near-field region. Most electromagnetic energy in this region is not radiated but is stored. This stored energy is transferred periodically between the antenna and the near field. The reactive near field region extends from the antenna up to a distance "R".  R  ---------------------------------------------2.3 2 where "λ" is the wavelength in meters (m). . For antennas large in terms of wavelength, the near field region consists of the reactive field extending to the distance given by Eq. (2.3), followed by a radiating region. In the radiating near field, the field strength does not necessarily decrease steadily with distance away from the antenna, but may exhibit an oscillatory character. The energy propagates away from the antenna, but the radiation still lacks a plane-wave character. Fig 2.2 shows field regions around an EM source. The far-field region, is the field region of an antenna in which angular field distribution is more or less independent of distance from the antenna. 14 University of Ghana http://ugspace.ug.edu.gh Figure 2.4 Field regions around an EM source In this region, the field has a predominantly plane wave character, i.e., local, very uniform distribution of electric and magnetic field strength in planes that are transverse to the propagation direction. The criterion commonly used to define the distance from the source where the far field begins is that the phase of the fields from all points on the radiating antenna does not differ more than λ/16. The distance from the antenna corresponding to this criterion is: 2a 2 R  (2.4)  Where " a " is the greatest dimension of the antenna. For a paraboloidal circular-cross-section antenna, a realistic estimate for "R", which provides close agreement with experimental results, can be obtained using the following relationship: a 2 R  0.5 (2.5)  where "a" denotes the antenna diameter. 15 University of Ghana http://ugspace.ug.edu.gh Figure 2.5 Near and Far-Field Nomenclature (ICNIRP, 2009) Towards the end of the radiating near field region and in the far field, the electric field strength (E), in volts per metre (V/m) and magnetic field strength (H), in amperes per metre (A/m) are interrelated with each other and the power density as: E  (2.6) H and E 2 W   H 2 (2.7)  where  =377 i.e. characteristic impedance of free space (safety code 6). 2.4.2.3 Polarization The orientation of an electric field vector and/or the magnetic field vector in the plane orthogonal to the direction of propagation is called polarization. The polarization may be constant in a particular direction (linear polarization) or rotating (elliptical polarization). If the electric field vector is always oriented in a given direction, the 16 University of Ghana http://ugspace.ug.edu.gh wave is linearly polarized (ICNIRP, 2009). If the electric field vector rotates around the direction of propagation, maintaining a constant magnitude, the wave is circularly polarized. If the extremity of the electric field vector traces an ellipse, the wave is elliptically polarized. The rotation of the electric field vector occurs in one of two directions, either clockwise or counter-clockwise. It is difficult to predict the orientation of the electric field in the near field region, as the transmitting antenna cannot be considered as a point source in this region. In the far field region, the antenna becomes a point source, the electric and magnetic components of the field become orthogonal to the direction of propagation and their polarization characteristics do not vary with distance (Health Canada, 2009). 2.4.2.4 Radiation pattern Electromagnetic waves are radiated into space via antennas. The radiation pattern generated by the source is the spatial distribution of the EM field with respect to the source and it determines the spatial distribution of the radiated energy. ICNIRP iterates that in the near-field, angular field distributions change greatly as a function of distance from the source. In the far-field, there should be no significant change in the angular field pattern with distance from the source, but reflecting objects in the far-field often make this assumption incorrect (ICNIRP, 2009). A pattern taken in the plane containing the electric field vector is referred to as an E- plane pattern. A pattern taken in a plane perpendicular to an E-plane is called an H- plane pattern. The directional pattern of an antenna describes how much it concentrates energy in one direction in preference to radiation in other directions (Health Canada, 2009). 17 University of Ghana http://ugspace.ug.edu.gh 2.5 Exposure categories The ANSI/IEEE standard and the NCRP exposure criteria upon which the FCC guidelines are based, recommend limits with respect to both occupational/controlled and general population/uncontrolled exposures. According to the FCC, the compliance requirements for both occupational/controlled and general population/uncontrolled exposures are based on a person's awareness and ability to exercise control over his or her exposure (FCC, 2009). 2.5.1 Occupational exposure In general, occupational/controlled exposure limits are applicable to situations in which persons are exposed as a consequence of their employment, who have been made fully aware of the potential for exposure and can exercise control over their exposure. This exposure category is also applicable when the exposure is of a transient nature due to incidental passage through a location where the exposure levels may be higher than the general population/uncontrolled limits, but the exposed person is fully aware of the potential for exposure and can exercise control over his or her exposure by leaving the area or by some other appropriate means. Awareness of the potential for RF exposure in a workplace or similar environment can be provided through specific training as part of a RF safety program. If appropriate, warning signs and labels can also be used to establish such awareness by providing prominent information on the risk of potential exposure and instructions on methods to minimize such exposure risks (FCC, 2001). 18 University of Ghana http://ugspace.ug.edu.gh 2.5.2 Public exposure According to (FCC, 2001), public exposure limits are applicable to situations in which the public may be exposed or in which persons who are exposed as a consequence of their employment may not be made fully aware of the potential for exposure or cannot exercise control over their exposure. Members of the general public would come under this category when exposure is not employment-related; for example, in the case of a wireless transmitter that exposes persons in its vicinity. Warning labels placed on low-power consumer devices such as cellular telephones are not considered sufficient to allow the device to be considered under the occupational/controlled category and the general population/uncontrolled exposure limits apply to these devices 2.6 Standard for limiting exposure to EM fields Many national and international institutions have come out with guidelines and standards that provide safety limits for human exposure to EM fields. Although these documents differ in particulars, most documents have several basic principles in common. These include the use of basic limits and reference levels, the use of two-tier exposure limits: general public exposure and occupational exposure limits, averaging times, and separate consideration for exposure to low-frequency and high-frequency fields. 2.6.1 Guidelines of the International Commission for Non-Ionizing Protection (ICNIRP) ICNIRP guidelines are the most accepted guidelines for non ionizing radiations. They are endorsed by notable organizations such as the World Health Organization (WHO), the International Telecommunications union (ITU) and by more than 30 countries worldwide including health administrations and environmental organizations. These 19 University of Ghana http://ugspace.ug.edu.gh guidelines are given as a function of basic restrictions and reference levels and are a two-tier system made up of general public and occupational exposure limits. The basic restrictions are physical parameters which are necessary to assure that there will not be any adverse effect, but they are difficult to measure in the field. Hence the basic restrictions are related to the reference levels which are easy to measure at field and are obtainable from the basic restrictions by using computational models and measurement methods. 2.6.2 Standard of the Institute for Electrical and Electronic Engineers (IEEE) - 3 kHz to 300GHz The IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3kHz to 300GHz are aimed at protecting people against established adverse health effects in human beings linked to electric, magnetic and electromagnetic fields in the frequency range 3kHz to 300GHz. These recommendations are expressed in terms of basic restrictions (BRs) and maximum permissible exposure (MPE) values and are a system of two tiers consisting of action level and controlled -environmental exposure limits. These recommendations are not intended for the purpose of preventing interference with medical and other devices that may exhibit susceptibility to RF fields. The basic restrictions are exposure restrictions to electromagnetic fields based on the established health effects. The maximum permissible exposure values are derived from BRs and are limits on external fields and both induced and contact current. Both the basic restrictions and the MPE values incorporate safety factors that take into account uncertainties. They provide a margin of safety for all. It is possible to exceed 20 University of Ghana http://ugspace.ug.edu.gh an MPE while still complying with BRs because generally, the safety factors incorporated in the MPEs are greater than the safety factors in the BRs. 2.6.3 FCC Exposure Guidelines The FCC’s guidelines for Maximum Permissible Exposure (MPE) are defined in terms of power density (units of milliwatts per centimeter squared: mW/cm2), electric field strength (units of volts per meter: V/m) and magnetic field strength (units of amperes per meter: A/m). The FCC guidelines incorporate two separate tiers of exposure limits that are dependent on the situation in which the exposure takes place and/or the status of the individuals who are subject to exposure. The decision as to which tier applies in a given situation should be based on the application of the definitions of controlled/occupational and uncontrolled/general population exposures (FCC, 1997). In the far-field, in free space of a transmitting antenna, where the electric field vector (E), the magnetic field vector (H), and the direction of propagation can be considered to be all mutually orthogonal ("plane-wave" conditions). 2.6.3.1 Time and Spatial Averaging A fundamental aspect of the exposure guidelines is that they apply to power densities or the squares of the electric and magnetic field strengths that are spatially averaged over the body dimensions. Spatially averaged RF field levels most accurately relate to estimating the whole-body averaged specific absorption rate (SAR) that will result from the exposure are based on this concept. This means that local values of exposures that exceed the stated MPEs do not imply non-compliance if the spatial average of RF fields over the body does not exceed the MPEs. Further discussion of 21 University of Ghana http://ugspace.ug.edu.gh spatial averaging as it relates to field measurements can be found in Section 3 of Bulletin 65 and in the ANSI/IEEE and NCRP reference documents noted there (FCC, 1997) . Another feature of the exposure guidelines is that exposures, in terms of power density, E2 or H2, may be averaged over certain periods of time with the average not to exceed the limit for continuous exposure. As shown in Table 2.9, the averaging time for occupational/controlled exposures is 6 minutes, while the averaging time for general population/uncontrolled exposures is 30 minutes. It is important to note that for general population/uncontrolled exposures it is usually not possible or practical to control access or otherwise limit exposure duration to the extent that averaging times can be applied. In those situations, it would normally be necessary to assume continuous exposure to RF fields that would be created by the on/off cycles of the radiating source. Another important point to remember concerning the FCC’s exposure guidelines is that they constitute exposure limits (not emission limits), and they are relevant only to locations that are accessible to workers (or members of an amateur’s household) or members of the public. Such access can be restricted or controlled by appropriate means such as the use of fences, warning signs, etc., as noted above. For the case of occupational/controlled exposure, procedures can be instituted for working in the vicinity of RF sources that will prevent exposures in excess of the reference levels in the guidelines. An example of such procedures would be restricting the time an individual could be near an RF source or requiring that work on or near such sources be performed while the transmitter is turned off or while power is appropriately reduced. 22 University of Ghana http://ugspace.ug.edu.gh 2.7 Exposure Measurements 2.7.1 Exposure zone According to the International Telecommunication Union (ITU, 2004, 2008) if it is determined that an EMF exposure assessments is needed due to the presence of intentional emitters, then EMF exposure assessment must be performed for all locations where people might be exposed to EMF. The intent of such an exposure assessment is to classify potential exposure to EMF as belonging to one of the three following zones: I. Compliance zone: In this zone, potential exposure to EMF is below the applicable limits for both controlled/occupational exposure and uncontrolled/general public exposure at the operation frequencies. II. Occupational zone: In this zone, potential exposure to EMF is below the applicable limits for controlled/occupational exposure but exceeds the applicable limits for uncontrolled/general public exposure at the operation frequencies. III. Exceedance zone: In this zone, potential exposure to EMF exceeds the limits for both controlled/occupational exposure and uncontrolled/general public exposure at the operation frequencies. For many mobile base station cell sites, the exceedance zone and the occupational zone are not easily accessible to people. They are only accessible to workers under special circumstances, such as a personnel standing directly in front of an antenna. 23 University of Ghana http://ugspace.ug.edu.gh Figure 2.6 Exposure zones 2.7.2 Site Measurement Analysis Measurement sites should be selected so that there are no reflecting objects and as few overhead conductors (power and telephone lines, antennas, buildings with metal roofs or gutters) as possible within ten times the wavelength. It is necessary to clearly identify the measurement regions in order to restrict the measurements to only one of the components; electric (E) or magnetic (H) (Cruz, 2005). 2.7.3 Broadband measurement The broadband measurement is based on an electromagnetic field analyzer controlled with its probe which could be controlled by a portable computer. The exposure level could be given in root mean square (rms) or peak value in V/m, or W/m2. Owing to their limited sensitivity, broadband meters are often used for compliance assessment (Cruz, 2005). Broadband devices (such as the commonly used electric and magnetic probes) do not give information on frequency spectrum. 24 University of Ghana http://ugspace.ug.edu.gh Nevertheless frequency selective measurements on large bands are possible by using small broadband antenna (e.g., bi-conical, horn, etc.) or more sophisticated and expensive devices (ITU-T Rec. K.61, 2003). The probes consist generally of short- electrical dipoles (or loops) that detect the field. The corresponding current flows through a conductor wire (with high resistance). Isotropic probes measure the field components in the three orthogonal directions in space and calculate the magnitude of the resultant field strength and thus facilitate the assessment procedure. Broadband frequency range coverage depends on the meter and probe to be used. Broadband measurements are simple and less time consuming. However Broadband instruments are relatively insensitive and are unable to respond rapid signal changes due to modulation (Cruz, 2005). 2.7.4 Narrowband Measurements Narrow-band devices are generally antennas with flat antenna factors over limited spectrum ranges (e.g., the dipole antennas) and can be used for frequency selective measurement (ITU-T Rec. K.61, 2003). Narrow-band measurements allow distinctions between the specific contributions in the different frequency ranges. They are based on the use of a spectrum analyser in association with one or several different antennas according to the frequency range to evaluate; tuned dipoles, biconal dipoles (30-300MHz, 20-600MHz, 250-1000MHz), log-periodic antennas (200-1000MHz), horn antennas (1-1.8GHz), double ridge waveguide horn antennas (1-1.8GHz), among others. The sensitivity of narrow-band devices is higher than broadband system and they are frequency selective so it is possible to identify the source of the noncompliance in case it is. The equipment is however bulky, especially because of some antennas which are large and could be susceptible to wind load when 25 University of Ghana http://ugspace.ug.edu.gh mounted on a tripod (Cruz, 2005). Most of the antennas are directional and have to be rotated or positioned at a number of orientations in order to ensure all of the signals are detected properly. 2.7.5 Calibration requirements 2.7.5.1 Calibration factor For broadband probes, the calibration factor, CF, is defined by the following formula: 𝐸 𝐶𝐹 = 𝑟𝑒𝑓 (2.8) 𝐸𝑚𝑒𝑎𝑠 It is the ratio between the expected electric reference field strength (𝐸ref) and the value (𝐸meas) read on the PC or on a dedicated receiver unit. This factor is mainly a function of frequency and, in the presence of non-linearity error, of field strength. The CF is determined as a frequency function. For each frequency, the CF value shall be known with uncertainty less than 1 dB. Errors due to frequency interpolation are included in the tolerable uncertainty on CF (ITU-T K.61, 2008). 2.7.5.2 Antenna factor The antenna factor (AF) is defined for antennas and frequency-selective probes as the ratio: 𝐸 𝐴 = 𝑟𝑒𝑓𝐾 [𝑚 −1] (2.9) 𝑉 Where 𝐸𝑟𝑒𝑓 [V/m] is the electric field strength on the probe and V [V] is the voltage measured on the spectrum analyser. This factor is primarily a function of frequency but, in the presence of non-linearity error, it may depend on field strength, too. The 26 University of Ghana http://ugspace.ug.edu.gh AF is determined as a frequency function. For each frequency, the AF value shall be known with an expanded uncertainty (i.e., 95% statistical confidence) of less than 2 dB. The maximum tolerable uncertainty includes also the error due to frequency interpolation (when needed) (ITU-T K.61, 2008). 2.8 Numerical models and Theoretical Estimations Methods Theoretical estimations of radiofrequency (RF) exposure provides a less stressful way of assessing the level of power density in far field region of a base station, but since RF radiation varies significantly from point to point due to absorption, reflection and local amplification from buildings and vegetation in an area, its result may vary significantly from the actual power density (Saeid and Ahmed, 2011; EPRI, 2011). The accuracy and quality of the calculations will depend on the analytical or numerical method used and on the accuracy of the description of the electromagnetic source(s) and physical objects between the radiator and the prediction point that may affect the fields. For SAR calculations, the accuracy of the body model will also affect the quality of the results. To be able to make a calculation, the source parameters have to be known or estimated. Examples of source parameters are frequency, mean power, peak power, pulse width, pulse length, pulse repetition rate, antenna pattern, gain and geometry. 27 University of Ghana http://ugspace.ug.edu.gh 2.8.1 Friis free space Friis free space equation can be used to calculate the power density in the far-field region of a transmitting source, where the EMFs are predominantly plane wave in character (ITU-R BS.1698, 2005). The Friis free space equation is generally accurate in the far-field of an antenna but will over-predict power density in the near field, where it could be used for making a "worst case" or conservative prediction (FCC, 1997). 𝑃𝐺 𝑆 = 2 (2.10) 4𝜋𝑅 P = Power G = Gain R = Radius 2.8.2 The point source model The point source method is a simple but very effective model which may be used in calculating the reference levels. It is assumed that the transmitting antenna is represented only by one point source, situated in the antenna electric centre and having a radiation pattern of the considered transmitting antenna. The accuracy of this model depends on the field region and on the antenna gain. This model is fully applicable in the far-field region (ITU-T Rec. K.70, 2007). 28 University of Ghana http://ugspace.ug.edu.gh 𝑃𝐺 𝐸𝐼𝑅𝑃 𝑆 = 𝐹(𝜃, ∅) = 𝑆 = 𝐹(2 2 𝜃, 𝜙) (2.11) 4𝜋𝑅 4𝜋𝑅 2.8.3 Ray tracing Ray tracing is useful for evaluation of fields in large open areas and in urban environments that involve multiple scatters. This model is accurate for open unbounded areas over flat earth. More complex scattering environments that involve reflections from building, fluctuations in earth elevations, etc., require complicated multi-ray algorithms. The ray tracing algorithms are most useful for exposure sufficiently far from the radiator where the fields reflected from buildings and the unevenness of the terrain are important. The main disadvantage of ray tracing is that it is essentially a far-field technique. Also, it assumes that the size of the antenna is large compared to the wavelength (ITU-T Rec K.61, 2008). 2.8.4 Two Ray model The two-ray model is a simplification of the ray tracing method and may be used when a single ground reflection dominates the multipath effect. The person being exposed will receive an E-field consisting of two components, the line of sight (LOS) component, which is the transmitted signal propagating through free space, and a non- line of sight (NLOS) component, which is the transmitted signal reflected off the ground. Moreover, the reflected E-field is proportional to the direct E-field, by a complex factor Γ (reflection coefficient), that has amplitude and phase. The complex 29 University of Ghana http://ugspace.ug.edu.gh Γ depends on the signal wavelength, polarization, surface’s permittivity and conductivity and incidence angle of the reflected ray (Agostinho et al, 2013). 𝐸𝐼𝑅𝑃 1 1 2 𝑆(𝑅, 𝜃, ϕ) = [𝑓(𝜃, ϕ) + |Γ|𝑓(𝜃′, ϕ′) ] (2.12) 4𝜋 𝑅 𝑅′ 2.8.4.1 Simple Two-Ray model Exposure at ground level The geometry for calculating exposure at the ground level due to an elevated antenna is shown in Figure 2.7 Figure 2.7 Sample configurations for calculating exposure at ground level (ITU K52) An antenna is installed so that the centre of radiation is at the height h above the ground. The goal of the calculation is to evaluate the power density at a point 2 m above the ground (approximate head level) at a distance x from the tower. In this example the main beam is parallel to the ground and the antenna gain is axially symmetrical (omnidirectional). 30 University of Ghana http://ugspace.ug.edu.gh Taking into accounts reflections from the ground, the power density becomes; 2.56 𝐸𝐼𝑅𝑃 𝑆 = 𝐹(𝜃 − 𝜙) (2.13) 4𝜋 𝑥2+ℎ′2 2.8.4.2 Simple Two-Ray Model Exposure at an adjacent building The geometry for calculating exposure at a building adjacent to an antenna tower is shown in Figure Figure 2.8 Sample configurations for calculating exposure at an adjacent building An antenna is installed so the centre of radiation is at the height h above the ground. The goal of the calculation is to evaluate the power density at a point 2 m above the roof level (approximate head level) of an adjacent building. The building has a height h2and is located at a distance x from the tower. The most severe exposure is expected at the edge of the roof closest to the antenna. It is assumed that the main beam is parallel to the ground and that the antenna gain is axially symmetrical (omnidirectional). In this situation, the reflections from the ground may be neglected 31 University of Ghana http://ugspace.ug.edu.gh since the reflected wave is likely to be attenuated by the building, so the power density becomes: 𝐹(𝜃−𝜙) 𝐸𝐼𝑅𝑃 𝑆 = 2 ′2 (2.14) 4𝜋 𝑥 +ℎ 2.8.5 Finite-difference time-domain method (FDTD) FDTD is a numerical method to solve Maxwell’s differential curl equations in the time domain. It is most useful for exposure assessment in near antenna or in confined locations with complex scattering environment and can be used to calculate internal and external EMF and SAR distribution in biological bodies for both near-field and far-field exposures. In FDTD, both time and space are discretized, and a biological body is modelled by assigning the permittivity and conductivity values to the space cells it occupies. The FDTD method offers great flexibility in modelling the heterogeneous structures of anatomical tissues and organs. The FDTD method can be used to predict field values in complex scattering environments by specifying appropriate boundary conditions or to predict SAR by specifying the dielectric properties and dimensions of the human body and appropriate boundary conditions for closed or open spaces (ITU-T Rec K.61, 2008). 2.8.6 Multiple-Region Finite-difference time-domain method (MR/FDTD) The MR/FDTD algorithm overcomes computational inefficiencies of FDTD for geometries that include extensive sparse regions. In MR/FDTD the problem space is divided into several independent sub regions distributed in an otherwise free space. 32 University of Ghana http://ugspace.ug.edu.gh The fields in the sub regions are determined with the use of localized FDTD lattices (ITU-T Rec K.61, 2008). 2.8.7 Methods of moment (MOM) The method of moments (MOM) [b-Harrington] is useful for evaluating the field strength emanating from antennas or other types of thin-wire conductive structures, and for computation of the scattered field from thin-wire metallic structures. The use of MOM for computation of scattering from conductive planar surfaces requires that such surfaces be represented by a wire mesh. MOM is useful for near-field and far- field computations. The details of the antenna construction and geometry and the geometry of scattering objects must be known. The MOM is not useful for determining field penetration through dielectric bodies and, therefore, is not suitable for determining SAR. Commercial and non-commercial implementations of MOM are available (ITU-T Rec K.61, 2008). 2.8.8 FDTD/ray tracing The hybrid FDTD/ray tracing technique tries to obtain the advantages of both methods. These methods use ray tracing to evaluate the incident field and FDTD to evaluate the SAR in the body (ITU-T Rec K.61, 2008). 2.9 Practical problems using Numerical Models and Theoretical Estimations The main practical problem in application of complex computational techniques, such as ray tracing or NEC is that the geometry needs to be specified precisely. In practice, the biggest obstacle to using even simple two-ray models is lack of adequate 33 University of Ghana http://ugspace.ug.edu.gh information about the antenna and the exposure environment. For example, the available terrain data may have limited resolution. Another example is when the antenna pattern provided by the manufacturer is valid for the far-field region. Near the antenna, the antenna gain may reduce and lobes may shift. One solution for this is to calculate the antenna patterns using MOM if the antenna construction is known (ITU-T Rec K.61, 2008). 2.10 Advantages of Numerical Models and Theoretical Estimations Numerical models and theoretical estimations are useful to predicting the level of the field strengths in a certain exposure situation in order to ascertain if measurements are needed and the equipment required. They can also be used to validate measurements and to verify that the obtained results from the measurements are reasonable. In other situations with complex near-field exposure conditions and expensive SAR measurement equipment is not available, calculations can replace measurements. The accuracy and quality of the prediction will rely on the analytical or numerical method used and on the accuracy of the description of the electromagnetic source(s) and physical objects between the radiator and the prediction point that may affect the fields. 2.11 Limitations of Numerical Models and Theoretical Estimations Very accurate estimations require detailed description of the radiating antennas and environment, and most models also do not take into account the influence of reflections. Lack of adequate information about antenna and the environmental 34 University of Ghana http://ugspace.ug.edu.gh exposure limits the use of numerical models and theoretical estimation. The point source model is fully applicable in the far-field region and hence gives over estimation when applied the near-field region. Ray tracing is not suitable for calculation at long wavelengths, where diffraction is important. 2.12 Assessment of Radiofrequency Exposure using numerical model and theoretical estimation methods. Cruz, 2005 used the two-ray tracing model to estimate the power densities from two different mobile base stations at Lima in Peru. A base station with sectorial antennas mounted on top of a 12m tower which in turn located on an 18m building and transmitting at a frequency of 800MHz. The base station has a three sector antenna arrangement at 8° down tilt and EIRP of 39 dBm for each sector. Cruz, 2005 estimated that the power density at distance of 15m away from the base station was 3.7329 × 10−6 𝑊/𝑚2. Power density on a 9m building at a distance of 50m from the base station was 2.25 × 10−5 𝑊/𝑚2. Both estimations were made at a reference height of 2m and were below the ICNIRP exposure limits. For a base station that works in the frequency band of 1900 MHz and is sectorial antennas mounted on top of a 35m tower, a 4° down tilt and EIRP of 55 dBm, the power density at a distance of 50m away from the antenna was 7.3768 × 10−4 𝑊/𝑚2. Power density on top a building 9m at 30m from the antenna was 1.36067 × 10−3 𝑊/𝑚2. 35 University of Ghana http://ugspace.ug.edu.gh 2.13 Assessment of Radiofrequency Radiation within the Vicinity of Some GSM Base Stations in Ghana. Assessment of radiofrequency radiation from mobile base stations has been carried in some parts of Ghana. Amoako et al (2009) report a survey of the radiofrequency electromagnetic radiation at public access points in the vicinity of 50 cellular phone base stations in Ghana. Amoako et al (2009) pointed out that “the selected sites were chosen to cover those close to schools, hospitals and highly populated residential areas”. Measurements were made at public access locations at all the sites. The primary objective was to measure and analyse the electromagnetic field strength levels emitted by antennae installed and operated by the Ghana Telecommunications Company and to assess the level of compliance with standards set by the International Commission on Non-ionizing Radiological Protection (ICNIRP) and other international regulatory bodies (Amoako et al., 2009). An Anritsu model MS 2601A hand held spectrum analyser was used. The results of field measurements at various cell sites used for this study show power density variation of as low as 0.01 µW m−2 to as high as 10 µW m−2 for the frequency of 900MHz. At a transmission frequency of 1800 MHz, the variation of power densities is from 0.01 to 100 µW m−2 (Amoako et al., 2009). Even though the ground level power densities were below the limits recommended by RF safety standards, the results however shows that in some cases the power densities measured are much higher (about 20 times higher) than typical values measured in other studies in the UK, Australia and the USA. Amoako et al (2009) stated that ”these results are quite important and give room for serious concern as the number of mobile phone users increases without a corresponding increase in the number of base stations. Emission 36 University of Ghana http://ugspace.ug.edu.gh levels are bound to go higher. There is a need to increase the number of cell sites in order to improve the quality of signal received at a lower antennae power level”. 2.14 Review of Studies on Assessment of the Levels of Radiofrequency Fields in the Vicinity of FM Radio Stations in Accra, Ghana. A survey of the RF electromagnetic radiation at public access points in the vicinity of 20 frequency-modulated (FM) radio stations has been made in Accra, Ghana to determine the levels of RF fields from FM broadcast antennae within 10-200 m radius about the foot of the FM base station (Azah et al 2013). Measurements were made at 10 different locations in each of the base station at a transmission peak period during the day. A spectrum analyser, Anritsu Spectrum Master MS2721B, was used. The spectrum master was connected via an antenna cable to a bi-conical antenna: BBA 9103, Bi-conical Elements with a serial number VHA 9103. The bi-conical antenna was mounted on a non-conductive tripod and connected via a lead-shielded coaxial cable to the Anritsu Spectrum Master MS2721B. The levels of electric field strength ranged from 5.4E-04 Vm-1 to 7. 4E-08 Vm-1 at a transmission frequency range of 88-108 MHz, the variation of power densities is from 2.5E-10Wm-2 to 1.5E-17 Wm-2 (Azah et al 2013). The results obtained showed a general compliance with International Commission for Non-Ionizing Protection (ICNIRP) reference levels and agreed to some extent with other results from similar works conducted in the UK. 37 University of Ghana http://ugspace.ug.edu.gh 2.15 Review of Comparative Studies Between the ITU-T Prediction Model For Radiofrequency Radiation Emission and Real Time Measurements at Some Selected Mobile Phone Base Stations in Accra, Ghana. A report on the survey of the radiofrequency electromagnetic radiation at public access points in the vicinity of 30 mobile phone base stations in Accra, Ghana were assessed and compared with the ITU-T prediction model (Obeng et al 2014). Measurements were made at 10 different points in each of the mobile base station at a distance of 20m from each point. An Anritsu model, MS2721B hand held spectrum analyser coupled to an Anritsu log periodic antenna, MP666A was used. The results of field measurements at various base stations used for this study show power density variation of 0.00961µW/m2 to 1.86µW/m2 for the frequency of 900MHz. The measured data was compared to that of the ITU-T predictive model which varies from 6.40mW/m2 to 0.344W/m2 at the same distance for the 15 selected mobile base stations (Obeng et al 2014). The results obtained showed a variation between measured power density levels and the ITU-T predictive model. The ITU-T model power density levels decrease with increase in radial distance (inverse square law) while real time measurements do not due to fluctuations during measurement (Obeng et al 2014). The ITU-T predictive model overestimated the power density levels of the real time measured data. The results were within the International limit and were lower when compared with work conducted on most of the same mobile base stations in Accra, Ghana. 2.16 An Engineering Assessment of the Potential Impact of Federal Radiation Protection Guidance on the AM, FM, and TV Broadcast Services. Paul C. Gailey and Richard A. Tell in 1985 report, described an engineering analysis of the potential impact of the proposed EPA federal Radiation Protection guidance for 38 University of Ghana http://ugspace.ug.edu.gh radiofrequency radiation on the broadcast industry. The study was performed by developing computer models of the radiofrequency radiation on the ground near broadcast stations and applying the models to data bases of the station. The models were developed using theoretical predictions, empirical data and existing numerical electromagnetic code, and compared with field study data and other prediction techniques to determine their accuracy. Holaday Industries Model 3001 electric field strength meters were used to make the measurements. Measurements were made around six FM stations and the measured field strength values were plotted as free-space equivalent power densities for comparison with the FM model output for those stations (Gaily & Tell, 1985). The FM model however, overestimated the measured data. Figure 2.9 Sample of calculated and measured power densities (free-space equivalent) for an actual FM station (Gailey & Tell, 1985) 39 University of Ghana http://ugspace.ug.edu.gh 2.17 Review of studies on Occupational Exposure 2.17.1 Cancer Information on cancer risks in relation to occupational RF exposure comes from three types of epidemiological study: cohort studies, investigating a wide range of cancer (and non-cancer) outcomes in groups with potential RF exposure; case-control studies of specific cancer sites, investigating occupational RF as well as other exposures and analyses of routinely collected datasets on cancer incidence or mortality, in which risks of cancer have been assessed in relation to job title. The most extensive literature addresses brain tumours and leukaemia (ICNIRP, 2009). Two US case-control studies of brain tumour aetiology have shown elevated odds ratios of around 1.5 in relation to jobs believed to have RF exposure. However, the study by Thomas et al (1987) was based on interviews with relatives of dead cases, and hence was unable to identify exposure with much certainty. The other study (Grayson, 1996) assessed exposures by a job exposure matrix based on historical reports of incidents of exposure above permissible limits (10mW/cm2). Several studies have investigated the risk of breast cancer in relation to RF exposure. A cohort study of radio and telegraph operators in Norwegian merchant ships by Tynes et al, 1996 found a relative risk of breast cancer of 1.5, based on 50 cases in women working in this occupation, stronger for women aged 50 and above. A study of US embassy personnel with potential RF exposure found 2 breast cancers with 0.5 expected (Goldsmith, 1995). Other studies of male and female (Morgan et al., 2000) breast cancers, with few cases, did not report increased risks. The available data are insufficient to reach any conclusion on whether RF exposure is related to breast cancer risk, but the results of Tynes et al, 1996 do support continued evaluation of the possibility. In conclusion, 40 University of Ghana http://ugspace.ug.edu.gh there is no cancer site for which there is consistent evidence, or even an individual study providing strong evidence, that occupational exposure to RF affects risk. The quality of information on exposure has generally been poor, however, and it is not clear that the heterogeneous exposures studied can be regarded as a single etiological entity. This combined with imprecision and methodological limitations leave unresolved the possibility of an association between occupational RF and cancer (ICNIRP, 2009). 2.17.2 Other outcomes A wide range of potential reproductive consequences of RF exposure have been investigated with a focus on exposures of physiotherapists to therapeutic short wave diathermy (typically 27.12 MHz) (ICNIRP, 2009). Depending on the type of equipment used and the location of the operator in relation to the equipment, substantial peak exposures can occur (Larsen & Skotte, 1991a). Many of the studies analysed levels of exposure, on the basis of duration of work and type of equipment used (shortwave or microwaves). There are isolated suggestions of an association between RF exposure and delayed conception (Larsen et al., 1991b), spontaneous abortion (Ouellet-Hellstrom and Stewart 1993; Taskinen et al., 1990), stillbirth (Larsen et al 1991b), pre-term birth with exposure to fathers (Larsen et al., 1991b), birth defects in aggregate (Larsen, 1991), and increased male to female sex ratio (Larsen et al., 1991b). Almost always, however, either the finding was not corroborated in other studies of comparable quality or there are no other studies available. 41 University of Ghana http://ugspace.ug.edu.gh The literature on RF and cardiovascular symptoms and disease provides little suggestion of an association, but is at too rudimentary a level to draw firm conclusions (ICNIP, 2009). Putative alterations in some cardiovascular parameters with RF exposure in an epidemiologic setting have not been replicated in exposed volunteers under experimental conditions (Jauchem, 1997,2008), and a neurological study in Sweden found no measurable differences in blood-brain barrier integrity among frequent users of wireless telephones (short- or long-term) compared with infrequent users (Soderqvist et al., 2009). All-cause mortality among Belgian military personnel who were radar operators for many years showed no increase compared with their counterparts who were never exposed to radars (Degrave et al., 2005). Finally two recent and extensive reviews have found no substantive evidence of adverse health outcomes arising as a result of high levels of RF exposure (Valberg et al., 2007; Jauchem, 2008). 42 University of Ghana http://ugspace.ug.edu.gh CHAPTER THREE MATERIALS AND METHODS 3.1 Introduction This chapter describes the materials and methods used for the research work. The field measurements were done during operating peak periods of FM installations. Power densities were calculated using the data from the on-site measurements. Numerical predictive model was developed to estimate the power density levels using the antenna physical parameters. 3.2 Sampling Ten (10) FM radiating antennas were selected within the Greater Accra Region and the Eastern Region of Ghana according to their proximity to buildings, antenna parameters; mounting height, effective isotropic radiating power, and the population density around them. The information on the location and technical parameters of the antennas were provided by the National Communication Authority (NCA). Figure 3.2 shows the GPS location of selected FM antennas site used for the work using the ArcGIS software. Figure 3.1 Anritsu Spectrum Master MS2721B with PC 43 University of Ghana http://ugspace.ug.edu.gh 3.3 Measurement instrumentation 3.3.1 Anritsu Spectrum Analyser A spectrum analyzer called Anritsu Spectrum Master for RF and Microwave Handheld Instruments with serial number 0940037 and a model number of MS2721B was used. It is frequency selective and measures the electric or magnetic field strength from one or more sources in a “narrow” frequency band. Anritsu Spectrum Master displays and/or records the field strength versus frequency through the frequency range of interest. The spectrum master is sensitive to RF within the range 9 kHz – 7.1GHz. The spectrum master was connected via a lead shield coaxial cable to a bi- conical antenna. 3.3.2 Bi-conical Element A BBA 9103 BICONAL ELEMENTS with serial number VHA 9103-2731 manufactured by SCHWARZBECK MESS-ELEKTRONIK was used. The bi-conical element is sensitive and effective within the Frequency Band of 30 -300MHz. The antenna cables used was a coax-cable which was matched to the receiver input impedance as well as to the antenna load impedance of 50Ω. The bi-conical element was mounted on a non-conductive antenna tripod. 3.3.3 Garmin Oregon 200 GPS The Oregon 200 GPS manufactured by Garmin Company was used in recording the coordinates of locations of the FM radiating antennas and the measurement points. 44 University of Ghana http://ugspace.ug.edu.gh The equipment set was made available by the Radiation Protection Institute of the Ghana Atomic Energy Commission which is located at Kwabenya, Accra. Figure 3. 2 Location of FM antennas using the ArcGIS software. 45 University of Ghana http://ugspace.ug.edu.gh 3.4 Methodology 3.4.1 Measurement set-up The bi-conical antenna; BBA 9103 BICONAL ELEMENTS 30MHz to 300MHz with a 50Ω 1:1 Balun VHA 9103 was mounted to the non-conductive tripod and was connected via a lead shielded coaxial cable to the Anritsu Spectrum Master MS2721B. The equipment was set up by using the appropriate parameters on the Spectrum Master; Bandwidth (BW) = 100kHz with a sweep time of 100ms, frequency span, Attenuation level (dBm) and scale as appropriate. The set up was allowed five minutes to warm up and the personnel went few meters away from the antenna during measurements, in order not to perturb electromagnetic field. Measurement were made with the bi-conical element facing the radiating FM antenna. The effective height of the bi-conical antenna and the tripods is 1.5m above the ground level was recorded using the tape measure. Measurements were taken at any convenient location around the radiating FM antenna. Fig 3.1 shows the Anritsu Spectrum Master MS2721B with PC. 3.4.2 Measurement of coordinates For repeatability of this research work, a satellite navigation system Global Positioning System GPS, known as the Oregon 200 GPS manufactured by the Garmin Company was used in recording the coordinate of the locations where measurements were made as well as the locations of the various antennas. The ArcGIS software was used in plotting and determining the distance of each test point from the radiating FM antenna. Below shows the location and test points of each radiating antenna under study using the ArcGIS software. The ArcGIS software is an enabling system for 46 University of Ghana http://ugspace.ug.edu.gh working on maps and geographic information using the Geographic Information System (GIS). Fig. 3.3 shows the coordinates and test points of Asempa FM radiating antenna using the ArcGIS software. 3.4.3 Determination and Documentation of the Test point(s) Measurement points within the vicinity of the each FM radiating antenna was determined based on the layout. Measurement points were chosen to represent the highest levels of exposure to which a person might be exposed considering the positions of the antennas. Measurement sites were selected so that there are few reflecting objects and as few overhead conductors (power and telephone lines, 47 University of Ghana http://ugspace.ug.edu.gh antennas, buildings with metal roofs or gutters) as possible. These locations were noted by a quick check using measuring equipment. Each measurement test point was recorded 1.5m above ground level using the tape measure. 3.4.4 Measurement of electric field The Bi-conical antenna was rotated in various directions until the highest peak was noted on the spectrum master. The transmitter signal was recorded over a six minutes period as a DAT file on the Spectrum master. Fig 3.4 shows a sample DAT file for location ‘A2’ of Marahaba 99.3MHz FM. Source: Field work 2016 Plate 3.1: Spectrum Analyser in use with bi-conical element (Star 103.5MHz FM) 48 University of Ghana http://ugspace.ug.edu.gh Source: Field work 2016 Plate 3.2 A typical FM radiating antenna (Marahaba 99.3MHz FM) 3.4.5 Determination of field strength The maximum peak corresponding to the frequency of interest was marked using the Spectrum Analyzer Software Tools. The frequency was set from 87 MHz as the start frequency and 108MHz as stop frequency. The scales on the spectrum Master were changed in order to record the equivalent amplitude in units of dBµV/m. The electric field strength was obtained by converting the measured field strength in dBµV/m to V/m using equation 3.1. 49 University of Ghana http://ugspace.ug.edu.gh Source: Field work 2016 FIG 3.4 Spectrums for Location ‘A2’ of Marahaba 99.3MHz FM F = URX + K + Ak (3.1) Where F (dBµV/m) is the field strength level URX (dBµV) is the receiver input voltage across 50Ω 50 University of Ghana http://ugspace.ug.edu.gh K (dB/m) is the antenna factor Ak (dB) is the cable loss The field strength level F (dBµV/m) is converted to E (V/m) using the relation in equation 3.2 E (V/m) = (10-6)10F/20 (3.2) Where F (dBµV/m) is the field strength level. The power density at each location was calculated using equation 3.3 (FCC, 1997). E 2 S  (3.3) 377 where S = power density (W/m2) E = electric field strength (V/m) H = magnetic field strength (A/m) For the level of compliance, the ratio Smeas/Sicnirp was calculated for each location test point as well as facility, where Smeas is the value determined from equation 3.3 and Sicnirp is the value of existing maximum permissible emission level set by ICNIRP. 3.5 Electric field Spatial Average The Spatial average electric field strength values were calculated for each FM radiating antenna and a graph of electric field strength against stations were plotted. The spatial average electric field strengths were calculated from equation 3.4. n E 2i E i1spatial_ average  (3.4) n 51 University of Ghana http://ugspace.ug.edu.gh 3.6 Uncertainty Estimation. For the estimation of uncertainty, the measured uncertainty was evaluated for the electric field measurements taking into account each of the various sources of uncertainty in the measurements. The standard uncertainty u(xi) and the sensitivity coefficient ci was analysed for the estimate xi of each quantity. (In this case ci = 1). The combined standard uncertainty Uc(E) of the estimate E of the measurand is calculated as a weighted root sum square (r.s.s.): n 2 Uc(E) = c *u   (3.5)  i xi  i1 The combine standard uncertainty Uc(E) was first found by calculating the estimated standard deviation S, which is given by the formula n 2 x  xi S  i1 (3.6) n1 n xi Where x = i is the mean of the verification checks and n is the total number n of samples. The standard uncertainty u(xi) was calculated using the expression S u   (3.7) xi n Where n is the number of measurements, which is equal to 10. The expanded measurement uncertainty (confidence interval of 95%), Ue, is calculated as: Ue±95% = x ± t0.95,n-1 Uc(E) = 1.96 Uc(E) (3.8) 52 University of Ghana http://ugspace.ug.edu.gh where x is the mean of the verification checks, t0.95,n-1 is the 95th quartile of a t-distribution with n-1 degrees of freedom, and Ue±95% is the 95% confidence range of the mean verification checks. The hybrid uncertainty is given by 2 2 2 σhybrid = U   (3.9) e a b where Ue is the type A uncertainty found through the standard deviation of the mean verification checks, σa is the type B uncertainty for the field instrument of interest σb is the uncertainty associated with the calibration standards. A normal probability distribution was assumed for all sources of uncertainty. The electric field intensity was recorded as E  σhybrid and was in units of V/m. This recorded uncertainty is based on a standard uncertainty multiplied by the coverage factor of 1.96 which yields a 95% level of confidence for the near-normal distribution typical of most measurement results. The uncertainty analysis is based on reference [ECC RECOMMENDATION, 2007)] 3.7 Numerical Prediction Model. The Two Ray Model was used as the basis for developing of the Numerical Predictive Model in predicting the power density levels of the FM radiating antennas. Insufficient information on the technical parameters of the FM radiating antennas and other environmental conditions precluded the possibility of detailed theoretical predictions for each source. The model was therefore designed to estimate the maximum, practically expected power density levels in order to compensate for the variety of condition that may exist near an FM radiating antenna. This implies that the model may significantly over-predict the power density levels in a particular test point 53 University of Ghana http://ugspace.ug.edu.gh and thus represent a conservative approach to dealing with a potential exposure to RF emission. A normal characteristic FM radiating antenna consist of one to sixteen element in a vertically stacked broadside array. A particular element vary in shape and radiation pattern in accordance with the manufacturer’s model. The elements are usually side mounted on a metallic tower or may be seen at the centre mounted on top of the tower. Plate 3.2 shows a typical FM radiating antenna. The minimum and maximum mounting height of the FM antenna was ranged between 39m to 65m respectively. The Effective Isotropic Radiated Power in antenna measurements, measures radiated power in a single direction (that is for a fixed azimuth or elevation angle). It is the energy in the antenna’s main beam. The EIRP is calculated using the antenna’s absolute gain referenced to an ideal isotropic radiator multiplied by the power actually required by the antenna. The single EIRP value given is the maximum value of EIRP value over all measured angle (including vertical and horizontal polarization). The minimum and maximum EIRP values ranged between 2,014.849W and 43,000W respectively. Consideration of ground reflection is important in impact modeling since field strength can be significantly increased. (Gailey & Tell, 1985). Paul C. Gailey and Richard A. Tells in 1985 worked on an engineering assessment of the potential impact of federal radiation protection guidance on AM, FM and TV broadcast antenna and estimated the ground surface reflection coefficient (𝜌 ) as 0.6 which was adopted in the model. Appendix C shows the gain, power to antenna, antenna mounting height and the EIRP and the assigned frequency for each FM station. For FM radiating antenna, the approximate power density radiated in the direction described by the 54 University of Ghana http://ugspace.ug.edu.gh angles θ (complementary to the elevation angle) and φ (azimuth angle) at a distance R and using the Two Ray model as the basis is given by the expression; Figure 3.5 Schematic diagram for calculating exposure at ground level 𝐸𝐼𝑅𝑃 1 1 2 𝑆(𝑅, 𝜃, 𝜙) = [𝑓(𝜃, 𝜙) + 𝜌𝑓(𝜃′, 𝜙′) ] (3.10) 4𝜋 𝑅 𝑅′ Where: S(R, θ,𝜙) is the power density in W/m2; f (θ,𝜙) is the relative field pattern of the antenna ; 𝑓(𝜃′, 𝜙′) is the relative field pattern of the antenna for the reflected signal; 55 University of Ghana http://ugspace.ug.edu.gh EIRP is the Equivalent Isotropically Radiated Power of the antenna in W; R is the distance between the antenna and the reference point; R' is the distance between the image of the antenna and the reference point; ρ is the absolute value (modulus) of the reflection coefficient and taking into account the wave reflected by the ground. First assumption: For reference points near the ground level, the values of primed variables are approximately equal to the unprimed, 1 1 𝑓(𝜃′, 𝜙′) ≅ 𝑓(𝜃, 𝜙) (3.10a) 𝑅′ 𝑅 𝐸𝐼𝑅𝑃 1 1 2 𝑆𝐺(𝑅, è, 𝜙) = [𝑓(𝜃, 𝜙) + 𝜌𝑓(𝜃, 𝜙) ] (3.11) 4𝜋 𝑅 𝑅 𝐸𝐼𝑅𝑃 1 2 𝑆𝐺(𝑅, 𝜃, 𝜙) = [𝑓(𝜃, 𝜙) (1 + 𝜌)] (3.12) 4𝜋 𝑅 𝐸𝐼𝑅𝑃 𝑆𝐺(𝑅, 𝜃, 𝜙) = [𝑓(𝜃, 𝜙) 2(1 + 𝜌)2] (3.13) 4𝜋𝑅2 𝑆 (𝑅, 𝜃, 𝜙) = (1 + 𝜌)2 𝐸𝐼𝑅𝑃 𝐺 ( ) 2 2 𝑓 𝜃, 𝜙 (3.14) 4𝜋𝑅 Further Assumptions: 1. Each FM radiating antenna is considered as a single site in case of the antennas located on the same tower. 2. All the FM radiating antennas under study were considered to be half-wave 𝜋 2 𝑐𝑜𝑠 𝑠𝑖𝑛 𝜃 dipole hence the relative numerical gain is calculated by 𝐹(𝜃) = [ 2 ] cos 𝜃 (ITU-T K.52, 2004) 56 University of Ghana http://ugspace.ug.edu.gh 3. For ground level exposure, an absolute value of 0.6 for the ground surface reflection coefficient (𝜌 ) is assumed. (Gailey & Tell, 1985) 4. A total nominal EIRP (including all polarisation) for each FM radiating antenna is considered. Rearranging and inserting the assumptions gives 𝑇𝑜𝑡𝐸𝐼𝑅𝑃 𝑆𝐺(𝑅, 𝜃) = (1 + 0.6) 2 ( )2 2 𝑓 𝜃, 𝜙 (4.0) 4𝜋𝑅 0.64 𝑇𝑜𝑡𝐸𝐼𝑅𝑃 𝑆𝐺(𝑅, 𝜃) = 𝑓(𝜃, 𝜙) 2 2 (4.1) 𝜋𝑅 The relative field pattern 𝑓(𝜃, 𝜙) is related to the relative numeric gain 𝐹(𝜃, 𝜙) as: 𝑓(𝜃, 𝜙) = √𝐹(𝜃, 𝜙) (4.2) Hence 𝑓(𝜃, 𝜙)2 = 𝐹(𝜃, 𝜙) (4.3) Now the Power Density at ground level, 𝑆𝐺 is given by 0.64 𝑇𝑜𝑡𝐸𝐼𝑅𝑃 𝑆𝐺(𝑅, 𝜃) = 2 𝐹(𝜃, 𝜙) (5.0a) 𝜋𝑅 Now assuming a person of height 1.5m standing at a distance X from a radiating FM broadcasting antenna as shown in figure 2; Therefore the Power Density will then be calculated as 57 University of Ghana http://ugspace.ug.edu.gh 𝟎.𝟔𝟒 𝑻𝒐𝒕𝑬𝑰𝑹𝑷 𝑆𝐺(R, θ) = 𝟐 𝟐 𝑭(𝜃) (5.0) 𝝅(𝒙 +𝒉 ) Since; R2 = x2 +h2 (5.1) h = H – 1.5 (5.2) ℎ 𝜃 = 𝑡𝑎𝑛−1 ( ) (5.3) 𝑥 The Numerical modelled Power Density is given as 𝟎.𝟔𝟒 𝑻𝒐𝒕𝑬𝑰𝑹𝑷 𝑆𝐺(R, θ) = 𝑭( )𝟐 𝟐 𝜃 (5.0) 𝝅(𝒙 +𝒉 ) 3.8 Sample Calculation 3.8.1 Power Density for the Numerical Predictive Model At a distance of ‘A1’ 19m from Vision One radiating antenna with antenna mounting height, H of 50m and total nominal EIRP of 5971.608 Watts ,the power density at point ‘A1’ was calculated using equation 5.0 𝟎.𝟔𝟒 𝑻𝒐𝒕𝑬𝑰𝑹𝑷 𝑆𝐺(R, θ) = 𝑭(𝜃) 𝝅(𝒙𝟐+𝒉𝟐) h = H - 1.5 h = 50 – 1.5 = 48.5m x = 19m ℎ 𝜃 = 𝑡𝑎𝑛−1 ( ) 𝑥 58 University of Ghana http://ugspace.ug.edu.gh Ɵ = 68.6071096° 𝜋 2 𝑐𝑜𝑠 𝑠𝑖𝑛𝜃 𝐹(𝜃) = [ 2 ] 𝑐𝑜𝑠𝜃 F (Ɵ) = 0.682963787 Tot EIRP = 5971.608 Watts SG (R, Ɵ) = 0.306216972 W/m 2 The results of the power density levels using the numerical predictive model at the various FM radiating antennas are shown in Appendix B2. 3.8.2 Real time measured power density For the test point ‘A1’ with a distance of 19m from Vision One radiating antenna, the field strength in dBµV/m across 50Ω was measured as 112.66dBµV/m. The field strength in dBµV/m was converted to the standardize electric field strength in units of V/m using equation 3.2 E (V/m) = (10-6)10F/20 E (V/m) = (10-6)10112.66/20 E (V/m) = 4.30E-01 V/m The power density of test point ‘A1’ in units of W/m2 was then calculated using equation 3.3 E 2 S  377 59 University of Ghana http://ugspace.ug.edu.gh (4.30E − 01 )2 𝑆 = 377 S = 4.89E-04 W/m2 The results of the power density levels at the various FM radiating antennas are shown in the Appendix B1. 3.8.3 Electric field Spatial Average For test point ‘A1’ 19m from the Vision One FM radiating antenna, the electric field spatial average was calculated using equation 3.4. n E 2i E i1spatial_ average  n ∑ 𝐸2 = 7.92349E - 01 n = 12 7.92349E − 01 𝐸𝑠𝑝𝑎𝑡𝑖𝑎𝑙 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 = √ 12 E spatial _average = 2.57E-01 V/m-1 The results of the electric field spatial averages are shown in the Appendix B3. 3.8.4 Exposure Quotient The (INCIRP, 1998) reference power density levels for occupational and general public exposure are 10Wm-2 and 2Wm-2 respectively. The occupational and general 60 University of Ghana http://ugspace.ug.edu.gh public exposure quotient of the test point ‘A1’ of Vision One FM radiating antenna was calculated as 𝑆 𝐸𝑥𝑝𝑜𝑠𝑢𝑟𝑒 𝑄𝑢𝑜𝑡𝑖𝑒𝑛𝑡 = 𝑀𝐸𝐴𝑆 𝑆𝐼𝐶𝑁𝐼𝑅𝑃 Where SMEAS = Calculated power density, SICNIRP = stipulated ICNIRP power density reference level. 4.89E−04 Occupational exposure quotient =( ) 10 = 4.83E- 05 4.89E−04 General public exposure quotient( ) 2 = 2.415E-04 3.8.5 Uncertainty Estimation The uncertain estimation for the Vision One FM radiating antenna was calculated as follow; The standard deviation was first calculated by employing equation 3.6 where n is the number of measurement points. n  2 x  xi S  i1 n1 n 2 x  x = 2.62E-01 i i1 2.62𝐸 − 01 𝑆 = √ 12 − 1 61 University of Ghana http://ugspace.ug.edu.gh S = 1.543E-01 Now the standard uncertainty was then calculated by employing equation 3.7 1.543𝐸 − 01 𝑈(𝑥 𝑖)= √12 U(xi) = 4.456E-02 The combined standard uncertainty Uc (E) was calculated using equation 3.5. in this case the sensitivity coefficient Ci , is given as Ci = 1 𝑼(𝒙 ) = 𝟒. 𝟒𝟓𝟔𝐄 − 𝟎𝟐 𝒊 𝑈𝑐(𝐸) = √(1 × (4.456E − 02))2 Uc(E) = 4.456E-02 The expanded measurement uncertainty was calculated by using the equation; Ue±95% = x ± t0.95,n-1 Uc (E) = 1.96 Uc (E) Hence Ue±95% = = 1.96 × 4.456𝐸 − 02 Ue±95% = = 𝟖. 𝟕𝟑𝟒𝑬 − 𝟎𝟐 The expanded measurement uncertainty for Vision One radiating antenna was calculated as 8.734E-02 62 University of Ghana http://ugspace.ug.edu.gh CHAPTER FOUR RESULTS AND DISCUSSION 4.1 Introduction This chapter discusses the results of the power density levels obtained from the real time measurements and validating it with the developed predictive model using the antenna physical parameters. Ten operational FM radiating antennas were surveyed and the predictive model used in validating the results for this research work. The developed predictive model was used to estimate power density levels for the FM broadcasting antennas whose antenna physical parameters were obtained. The average power density levels with their respective radial distances, electric field spatial average and exposure quotients are also discussed. The results from this research work have been compared to international standards. 4.2 FM radiating antennas Power density levels The power density levels of the FM radiating antenna at any point of interest depends on the effective isotropic radiating power at which the antenna is transmitting and the mounting height of the antenna. Most of the FM antennas employ in this research use Yagi antennas with a minimum and maximum Effective Isotropic Radiating Power range of 2014.849W to 39716.41W and mounting height range of 39m to 65m respectively. Appendix D presents graphs of the comparison of the measured and calculated power density levels. 63 University of Ghana http://ugspace.ug.edu.gh 4.2.1 Measured Power Density Levels Most of the antennas surveyed were located within residential settlements with some as near as 25m to nearby buildings and busy roads. Measured power density levels ranged from 1.01E-08W/m2 to 1.61E-02W/m2 as shown in Table 4.1. MARAHABA 99.3MHz FM REAL TIME MEASUREMENT 9.00E-04 8.00E-04 7.00E-04 6.00E-04 5.00E-04 4.00E-04 3.00E-04 2.00E-04 1.00E-04 0.00E+00 0 50 100 150 200 250 300 350 -1.00E-04 DISTANCE FROM TOWER (m) Fig. 4.1 Plot of power density against distance for Marahaba FM (real time measurement) 64 POWER DENSITY (W/m2) University of Ghana http://ugspace.ug.edu.gh Table 4.1 Maximum and Minimum Power density values of surveyed FM Stations Min. Max. Average Power Power Power density density density (W/m2) (W/m2) (W/m2) Vision One FM 5.80E-08 6.63E-04 1.75E-04 Marahaba FM 2.30E-06 8.50E-04 2.10E-04 Star FM 1.01E-08 4.50E-03 4.03E-04 Kasapa FM 4.20E-08 1.61E-02 1.37E-03 Live FM 3.14E-08 1.41E-02 1.34E-03 Oman FM 1.78E-08 2.98E-04 3.84E-05 Happy FM 1.10E-07 1.10E-03 1.35E-04 Y-FM 1.94E-07 1.66E-04 3.29E-05 Joy FM 1.70E-07 2.49E-04 3.92E-05 Asempa FM 1.22E-08 8.29E-05 1.08E-05 From observation, Kasapa 102.3MHz FM recorded the highest average power density level of 1.37E-03W/m2 compared to that of the values from other stations. Joy 99.7MHz FM recorded the least measured average power density level of 3.92E- 05W/m2. Other FM stations with significant high power density levels were Live 91.9MHz FM (1.34E-03W/m2), Star 103.5MHz FM (4.03E-04W/m2), Marahaba 99.3MHz FM (2.10E-04W/m2), Vision One 93.5MHz FM (1.75E-04W/m2) and Happy 98.9MHz FM (1.35E-04W/m2). Some of the surveyed FM stations recorded relatively lower levels of power density which can be attributed to the antenna parameters; mounting height, transmitting power and the radial distances. 65 University of Ghana http://ugspace.ug.edu.gh The highest power density level 1.61E-02W/m2 was measured at test point ‘A4’ at a distance of 10m away from the Kasapa FM radiating antenna whiles the least power density level 1.01E-08W/m2 was measured at test point ‘J3’ at a distance of 1,066m from the Star FM radiating antenna. The results of the measured power density levels at various FM stations are outlined in the Appendix B1. It was anticipated that power density levels will decrease by the square of the radial distance (inverse square law) as measurements were made at the various test points by increasing radial distances away from the reference radiating antenna. This was however not observe in most test points because significant fluctuations were observed in the data during measurement. These observations could be attributed to several factors such as, obstruction constituted by structures placed or erected within the line of sight of measurement, interference from radiation, noise from moving objects such as vehicles, motorcycles etc., and elevation of the land area around the reference radiating antenna with respect to radial distance away from antenna. Also the wave interference from other antennas clustered around a reference radiating antenna and the weather condition; humidity and temperature which were observed during measurement. 4.2.2 The Predictive model power density levels The developed numerical predictive model was used to estimate the power density levels by knowing the antenna’s technical parameters; total EIRP (vertical and horizontal), antenna mounting height, antenna gain and power to antenna from the constructor and the radial distance and position of the test point. The idea 66 University of Ghana http://ugspace.ug.edu.gh measurement method would be to maintain equal distances between the test point and the antennas for the FM radiating antennas. However, it was not possible to follow the above protocol exactly due to the buildings and terrain features which differs from site to site. The estimated minimum and maximum power density levels ranged from 5.99E-06W/m2 to 3.1289W/m2 as shown in Table 4.2. Power density levels vary with varying antenna parameters. With the same antenna height, power density levels increase with an increase in the EIRP and the corresponding power to antenna. Table 4.2 Maximum and Minimum Power density values (Numerical Predictive) Model) FM Stations Min. Max. Average Power Power density Power density (W/m2) density (W/m2) (W/m2) Vision One FM 8.33E-05 3.06E-01 3.84E-02 Marahaba FM 5.64E-05 7.42E-01 9.88E-02 Star FM 2.43E-04 3.1289 5.35E-01 Kasapa FM 8.15E-04 9.72E-01 1.77E-01 Live FM 5.99E-06 1.0229 1.63E-01 Oman FM 2.64E-04 2.0912 2.42E-01 Happy FM 3.97E-04 4.21E-01 9.12E-02 Y-FM 4.86E-05 7.07E-02 9.72E-03 Joy FM 3.65E-04 5.59E-02 1.80E-02 Asempa FM 1.14E-04 3.55E-01 8.14E-02 67 University of Ghana http://ugspace.ug.edu.gh Star FM broadcasting antenna recorded the highest average power density of 5.35E- 01W/m2 compared to that of the others due the fact that it recorded the highest power actually accepted by the antenna of 5000W (power to antenna) with a corresponding EIRP of 39716.41W and a relatively lower mounting height of 50m. Y-FM recorded the least average power density of 9.72E-03W/m2 due to the fact that it recorded the lowest EIRP of 2014.849W with a corresponding power to antenna of 900W and the highest antenna mounting height of 65m. Other FM stations with significantly high power density levels are Oman FM (2.42E-01W/m2), Kasapa FM (1.77E-01W/m2) and Live FM (1.63E-01W/m2). Although Asempa FM transmit at the highest EIRP value of 43,000W with a corresponding power to antenna of 4300W and a significant antenna mounting height of 50m recorded relatively lower power density of 8.14E- 02W/m2. This may be attributed to the type of antenna, number of elements, the radiation pattern and aperture dimension of the FM radiating antenna. It was however observed that between 100m radial distance, the power density levels decreases as the radial distance increases for most of the FM broadcasting antennas but recorded several fluctuations between radial distances after the 100m radial distance. Results of the estimated power density levels at various FM stations are presented in the Appendix B2. 68 University of Ghana http://ugspace.ug.edu.gh MARAHABA 99.3MHz FM NUMERICAL PREDICTIVE MODEL 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 50 100 150 200 250 300 350 -0.1 DISTANCE FROM TOWER (m) Fig. 4.2 Plot of power density against distance for Marahaba FM (Numerical Predictive Model) 4.3 FM model verification In order to validate and verify the accuracy of the FM numerical predictive model, a field study was conducted in two major regions in Ghana (Greater Accra and Eastern Region). Field measurements were made around ten FM stations which represent different types of antennas, EIRP’s, antenna mounting height and terrain. A graph of the measured field strength values were plotted as free-space equivalent power densities against the radial distances for comparison and validation with the output of the FM numerical predictive model as shown in Figure 4.3. 69 POWER DENSITY (W/m2) University of Ghana http://ugspace.ug.edu.gh MARAHABA 99.3MHz FM 8.00E-03 7.00E-03 6.00E-03 5.00E-03 4.00E-03 3.00E-03 2.00E-03 1.00E-03 0.00E+00 0 50 100 150 200 250 300 350 -1.00E-03 DISTANCE FROM TOWER (m) Real Time Measurement(W/m^2) Numerical Predictive Model (mW/m^2) Figure 4.3 Predictive model and real-time measured power densities of an actual FM station. It was observed that for the same FM antenna, the FM model estimates relatively higher power density levels as compared to that of the measured data output. The average power density for the numerical predictive model for Marahaba 99.3MHz FM was recorded as 9.88E-02W/m2 whiles that of the real time measurement for the same FM station at the same radial distances was 2.10E-04W/m2. The average power density levels of the FM model overestimated that of the measured data. Since the FM model predicts the maximum equivalent power density anticipated at each radial distance from the base of the tower to the height of the bi-conical element of 1.5m, efforts were made during measurements to reflect same concept for 70 POWER DENSITY University of Ghana http://ugspace.ug.edu.gh validation. The ideal measurement method would be to choose the same equally spaced radial distance for all the FM station. It was not possible to comply with the above protocol exactly at most of the measuring areas due to buildings and terrain features. However, each FM station site was assessed distinctively and compared to the corresponding FM model results. From Figure 4.3, it shows the graph of the numerical predictive model plotted along with the measured values for the station under study. Analysing these comparable graphs depict that the FM model curves are in good agreement with the measured data. The idea of the FM numerical predictive model is to estimate an upper bound of the real values of exposure to RF emissions at a particular FM station. It was observed in some situations that the measured values exceeded that of the predicted curves at certain test points. However, in all situations the maximum value estimated by the FM model was not exceeded by that of the measured data. This objective appears to have been met to an acceptable degree for the ten FM stations measured. The impact predictions were based on the maximum values estimated by the FM model, hence these results validates the credibility of the impact analysis for the FM stations. The average power density level values from the predictive model and measured data were both below the International Commission on Non-Ionizing Radiation Protection (ICNIRP) limit and other international standards. 4.4 Limitations of the model Any tool for prediction may not precisely define the real environment and terrain features. However, prediction tools have major merits than that of real time measurement. In the development of the numerical predictive model, one needs only 71 University of Ghana http://ugspace.ug.edu.gh to have the information of the antenna’s location, antenna mounting height, the power to antenna, absolute gain and the radial distance from the base of the tower to the test point. Additional data such as type of antenna, number of element, radiation pattern, losses, orientation and weather conditions however adds to the accuracy of the prediction values. Access to instrumentation, access to information from the constructor, and the time during the research were the reasons for which the additional data were not considered. All the same, efforts were made and further assumptions proposed in developing the FM model. 4.5 Electric field spatial average The electric field spatial average values were determined for each of the stations using equation 3.4. Kasapa FM recorded the highest spatial average of 7.17E-01 ± 6.97E- 01V/m whiles Asempa FM recorded the lowest spatial average of 6.39E-02 ± 5.39E- 02V/m. Live FM has relatively high electric field strength of 7.11E-01 ± 6.70E- 01V/m. Star FM, Marahaba FM and Vision One FM recorded significant values in the order; 3.90E-01 ± 3.66E-01V/m, 2.82E-01 ± 1.79V/m and 2.57E-01 ± 1.54V/m respectively. Other FM stations like Y-FM, Oman FM and Joy FM recorded relatively low spatial average of 1.11E-01 ± 8.12E-02V/m, 1.20E-01 ± 9.37E-02V/m and 1.22E-01 ± 1.01E-01V/m respectively. 72 University of Ghana http://ugspace.ug.edu.gh ELECTRIC FIELD SPATIAL AVERAGE INTENSITIES OF FM STATIONS 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 FM STATIONS Figure 4.4 Spatial average electric field strength of each FM station The variation in the electric field spatial average recorded could be attributed to factors such as reflection, diffraction as well as the antenna parameters including the transmitting power, height of the antenna, aperture dimension and the radial distance. Figure 4.4 displays spatial average electric field strength of each FM station. Appendix B3 shows the results of the electric field spatial average for the various FM stations. 4.6 Exposure quotient The exposure quotient is the ratio of power density levels determined in this research study to the MPE levels set by the ICNIRP. Exposure quotient is used to check compliance with national and international Limits. 73 ELECTRIC FIELD (V/m) University of Ghana http://ugspace.ug.edu.gh The MPE value recommended by ICNIRP for general public exposure and occupational public exposure are 2W/m2 and 10W/m2 respectively for FM stations. The maximum exposure quotient values determined should be unity. The maximum values recorded for this research are 2.68E-01 and 5.35E-02 for general public exposure quotient and occupational exposure quotient respectively. The exposure quotient at a base station should not exceed 1 for complying with maximum exposure limit recommended by ICNIRP. The highest values obtained were less than one (1) hence within the international acceptable limits. The exposure quotient values obtained in this study were relatively low due to the fact that the measurements were carried out in the far field regions of the various FM radiating antennas. Exposure quotient was calculated for each FM station using equation 3.4 as shown in Table 4.3. Table 4.3 Exposure quotients calculated from FM stations. FM Station Occupational General Public Exposure Exposure Quotient Quotient Vision One FM 3.84E-03 1.92E-02 Marahaba FM 9.88E-03 4.94E-02 Star FM 5.35E-02 2.68E-01 Kasapa FM 1.77E-02 8.85E-02 Live FM 1.63E-02 8.15E-02 Oman FM 2.42E-02 1.21E-01 Happy FM 9.12E-03 4.56E-02 Y-FM 9.72E-04 4.86E-03 Joy FM 1.80E-03 9.00E-03 74 University of Ghana http://ugspace.ug.edu.gh Asempa FM 8.14E-03 4.07E-02 4.7 Comparison with International Standards The results of measured power density levels in this study have been compared to the ICNIRP limits to check for compliance. The MPE value recommended by ICNIRP for general public exposure and occupational public exposure are 2W/m2 and 10W/m2 respectively for FM stations. The highest measured value of electric field occurred at test point ‘A4’ a distance of 10m from the Kasapa FM radiating antenna as 2.47Vm-1 with a corresponding power density of 1.61E-02W/m2. The results obtained depicts that the measured values for the electric field with their corresponding power density levels are far below the reference levels set for both general public and occupational exposures. 4.8 Comparison of results with other researched works. The obtained results from this survey was compared to other works done by Obeng et al in 2014 in Accra, Ghana, Azah et al in 2013 and Amoako et al in 2009. Obeng et al, survey was on the comparative studies between the ITU-T prediction model and real time measured data for thirty mobile base station within the vicinity of Greater Accra. The maximum and minimum average power density measured from individual base station is 1.86µW/m2 and 0.00961µW/m2 respectively for a frequency range of 900MHz. The ITU-T Predictive model power density values reported by Obeng et al, is estimated between 6.40mW/m2 and 0.344W/m2. Azah et al 2013 was done in the immediate vicinity of twenty FM radio stations. The range of power densities reported 75 University of Ghana http://ugspace.ug.edu.gh by Azah et al is between 2.5E-10 to 1.50E-17W/m2 at transmission frequency range of 88 to 108 MHz. For Amoako et al, survey was carried out at public access points in vicinity of fifty cellular phone base station in Accra, Ghana. The found results indicated that power density at public access points varied from as low as 0.01 to as high as 10 μW/m2 for frequency range of 900MHz. At a transmission frequency of 1800 MHz, the variation of power densities is from 0.01 to 100 μW/m2. The surveyed results obtained are higher compared to results reported by Azah et al, 2013 and a bit higher than the results of Amoako et al, 2009. The measured data and the developed predictive model values were a little higher than that of Obeng et al, 2014 but show compliance with ICNIRP guidelines. 76 University of Ghana http://ugspace.ug.edu.gh CHAPTER FIVE CONCLUSIONS AND RECOMMENDATIONS 5.1 Conclusions FM model has been developed and verified with real time measured data of ten FM radiating antennas in Ghana. The numerical predictive model developed for estimating the levels of RF radiation was verified with measured power density levels of ten FM radiating antennas within the two major regions in Ghana (Greater Accra and Eastern Region). Many assumptions were considered in the formulation of the numerical predictive model hence there can be no guarantee of the accuracy of the graphs. However, the real time measured data indicates that the model is a good estimation of the upper bounds of the equivalent power density levels occurring at the various test points near an FM radiating antenna. The FM model overestimates the power density levels as compared to that of the measured data. The average power density of the real time measured data ranged between 3.92E-05W/m2 and 1.37E- 03W/m2 whiles that of the FM model varied from 9.72E-03W/m2 to 5.35E-01W/m2. The highest measured power density level 1.61E-02W/m2 was measured at test point ‘A4’ a distance of 10m away from the Kasapa FM radiating FM. Test point ‘J3’ recorded the lowest power density level of 1.01E-08W/m2 at a distance of 1066m away from the Star FM radiating antenna. The maximum and minimum electric field spatial average recorded was 7.17E-01 ± 6.97E-01V/m at Kasapa FM and 6.39E-02 ± 5.39E-02V/m at Asempa FM respectively. The general public exposure quotient ranged between 9.00E-03 and 2.68E-01 whilst that of the occupational exposure quotient varied from 9.72E-04 to 5.35E-02. 77 University of Ghana http://ugspace.ug.edu.gh In spite of the fact that inevitable factors had an impact in the measurements, the measured values were found to be in conformity with the reference levels set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP), Institute for Electrical and Electronic Engineers (IEEE) and Federal Communications Commission (FCC). The results obtained from this research agrees favourably with other research works carried out by Obeng et al 2014, Azah et al 2012 and Amoako et al 2009 in some parts of Ghana. 5.2 Recommendations 5.2.1 Recommendation to National Communication Authority (NCA). The National Communication Authority should liaise with the telecommunication service providers to cooperate and or sponsor institutions like Ghana Atomic Energy Commission (GAEC) and other research scientists to carry out research into possible effect of RF radiation. . In the case of FM, TV and telecommunication mast sites, conduct an assessment of RF radiation levels within the localities and also evaluate the impact of RF radiation on the general public. 5.2.2 Recommendation to FM radio stations Proprietors of FM radio stations should allocate departments responsible for safe and secure use of RF radiating sources headed by a radiation protection officer (RPO). FM radio stations designers may consider design measures aimed at lowering electric field levels (exposure) while maintaining safe, secure and effective transmission of RF radiations. 78 University of Ghana http://ugspace.ug.edu.gh 5.2.3 Recommendation to Occupationally Exposed Workers Occupationally exposed workers can reduce their exposure to electric fields by observing the following principles; 1. Workers should have adequate knowledge about the antenna and the effects of RF radiation exposure and carry along with them personnel EMF monitors to alert them of potential over exposure within the near field 2. Transmission should be turned off before undertaking maintenance work on the antenna. 3. Workers should adhere strictly to the safety instructions provided by the manufacturer. 5.2.4 Recommendation to the General Public Members of the general public should take RF education seriously and adhere to the safety regulations. They are also to desist from the habit of leasing patches of lands located within heavily populated localities to be used as antenna sites for transmitting RF radiations. 5.2.5 Recommendation for Further Studies The following recommendations are being made for future study; 1. Research work should be carried out on all FM and TV station antennas as well as other telecommunication mast sites nationwide. 2. Estimation of RF exposure using other developed numerical predictive models and comparing the results to that of measured data. 79 University of Ghana http://ugspace.ug.edu.gh 3. Estimation of RF exposure using the FM model software of the FCC which was originally developed by the Environmental Protection Agency of the United State and the results compared with measured data. 80 University of Ghana http://ugspace.ug.edu.gh REFERENCE Agostinho Linhares, Marco Antonio Brasil Terada & Antonio José Martins Soares (2013). Estimating the Location of Maximum Exposure to Electromagnetic Fields Associated with a Radiocommunication Station. Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 12(1), 141- 157 Amoako, J.K, Fletcher, J.J. & Darko, E.O. (2009). Measurement and analysis of radiofrequency radiations from some mobile phone base stations in Ghana. Retrieved http://rpd.oxfordjournals.org/content/135/4/256/F1.expansion.html Aslan, E. (1972). Broadband Isotropic Electromagnetic Radiation Monitor. IEEE Trans.Vol. IM-21, No. 4, pp 421. Azah, C. K., Amoako, J. K., & Fletcher, J. J. (2013). Levels of electric field strength within the immediate vicinity of FM radio stations in Accra, Ghana. Radiation Protection Dosimetry, pp 1-6. Cember, H. and Johnson, T.E. (2009). Health Physics. 4th ed. The McGraw-Hill Companies, Inc. U. S. A. Cruz Ornetta V (2005), NIR Measurements; Principles and Practices of EMF characterization and measurements, National Institute for Research and Training in Telecommunications- Peruvian National University of Engineering (INICTEL-UNI) RC-11. Degrave, E., Autier, P., Grivegnée, A.R., & Zizi, M. (2005). All-cause mortality among Belgian military radar operators: a 40-year controlled longitudinal study. European Journal of Epidemiology, 20(8), 677-681. 81 University of Ghana http://ugspace.ug.edu.gh FCC Office of Engineering and Technology (2001). Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields. Supplement C Edition 01-01 to OET Bulletin 65. Edition 97-01. FCC Office of Engineering and Technology (2009). Exposure to Radiofrequency Electromagnetic Fields. Supplement A to OET Bulletin 65. Edition 97-01 Federal Communications Commission Office of Engineering and Technology (August, 1997). Evaluating Compliance with FCC Guidelines for Human 8. Gailey, P. C., and R.A. Tell, "An Engineering Assessment of the Potential Impact of Federal Radiation Protection Guidance on the AM, FM, and TV Broadcast Services," U.S. Environmental Protection Agency, Report No. EPA 520/6 85- 011, April 1985. NTIS Order No.PB 85-245868. Goldsmith, J.R. (1995). Epidemiologic Evidence of Radiofrequency Radiation (Microwave) Effects on Health in Military, Broadcasting, and Occupational Studies. International Journal of Occupational & Environmental Health, 1(1), 47-57; Grayson, J.K., (1996). Radiation exposure, socioeconomic status, and brain tumor risk in the US Air Force: a nested case-control study. American Journal of Epidemiology, 143, 480-486; Health Canada (2009) Limits of Human Exposure to Radiofrequency Electromagnetic Fields in the Frequency Range from 3kHz to 300GHz. Safety Code 6, Canada. Retrieved from http://www.hc-sc.gc.ca/ewh- semt/pubs/radiation/99ehd dhm237/index_e.html Incidence of breast cancer in Norwegian female radio and telegraph operators. Cancer Causes Control, 7(2), 197-204. 82 University of Ghana http://ugspace.ug.edu.gh International Commission on Non-Ionizing Radiation Protection (1998). Guidelines for Limiting Exposure to Time-varying Electric, Magnetic and Electromagnetic fields (up to 300 GHz). Health Phys 74(4):494-522, International Commission on Non-Ionizing Radiation Protection (2009) Exposure to High Frequency Electromagnetic fields, Biological Effects and Health Consequences (100 kHz – 300 GHz). Health Phys 74:494-522. ITU-R (2005). Evaluating fields from terrestrial broadcasting transmitting systems operating in any frequency band for assessing exposure to non-ionizing radiation. Series K: Protection against Interference, Recommendation BS. 2698 ITU-T (2004). Guidance on Complying with Limits for Human Exposure to Electromagnetic Fields. Series K: Protection against Interference, Recommendation K.52. ITU-T (2007). Mitigation techniques to limit human exposure to EMFs in the vicinity of radiocommunication stations. Series K: Protection against Interference, Recommendation K.70. ITU-T (2008). Guidance to Measurement and Numerical Prediction of Electromagnetic Fields for Compliance with Human Exposure Limits for Telecommunication Installations, Series K: Protection against Interference, Recommendation K.61. Jauchem, J.R. (1997). Exposure to extremely-low-frequency electromagnetic fields and radiofrequency radiation: cardiovascular effects in humans. International Archives of Occupational & Environmental Health, 70(1), 9-21. Jauchem, J.R. (2008) .Effects of low-level radio-frequency (3kHz to 300GHz) energy on human cardiovascular, reproductive, immune, and other systems: a review 83 University of Ghana http://ugspace.ug.edu.gh of the recent literature. International Journal of Hygiene & Environmental Health, 211(1-2), 1-29. Kitchen, R. (1999). Radio frequency and microwave safety handbook; Reed educational and professional publisher. Royal Society of Canada Expert Panel, 1999, PP 24 Larsen, A.I, & Skotte, J. (1991a). Can exposure to electromagnetic radiation in diathermy operators be estimated from interview data? A pilot study. American Journal of Industrial Medicine, 19(1), 51-57. Larsen, A.I., Olsen, J, & Svane, O. (1991b). Gender-specific reproductive outcome and exposure to high-frequency electromagnetic radiation among physiotherapists. Scandinavian Journal of Work Environment & Health, 17, 324-329. Miller, G.M. (1999). Modern Electronic Communication. 6th ed. Prentice- Hall International (UK) Limited, London. Morgan, R.W., Kelsh, M. A., Zhao, K., Exuzides, K.A., Heringer, S., & Negrete, W. (2000). Radiofrequency exposure and mortality from cancer of the brain and lymphatic/hematopoietic systems. Epidemiology, 11(2), 118- 27. Obeng, S.O, Amoako, J.K. & Fletcher, J.J. (2014). Comparative studies between the ITU-T Prediction model for radiofrequency radiation emission and real time measurements at some selected mobile phone base stations in Accra, Ghana. Unpublished manuscript. Ouellet-Hellstrom, R., & Stewart, W.F., (1993). Miscarriages among Female Physical Therapists who report using radio and microwave-frequency electromagnetic radiation. American Journal of Epidemiology, 138(10), 775- 786 84 University of Ghana http://ugspace.ug.edu.gh Saeid, S.H. and S.F. Ahmed. 2011. “Study and Assessment of Performance of Mobile Phones Base Stations Antennas Using MATLAB and TEAMS”. European Journal of Scientific Research. 53:249-257. Söderqvist, F., Carlberg, M., & Hardell, L., (2009) Use of wireless telephones and serum S100B levels: a descriptive cross-sectional study among healthy Swedish adults aged 18-65 years. Science of the Total Environment, 407, 798-805. Taskinen, H., Kyyronen, P., & Hemminki, K., (1990). Effects of ultrasound, shortwaves, and physical exertion on pregnancy outcome in physiotherapists. Journal of Epidemiology & Community Health, 44(3), 196-201. Thomas, T.L., Stolley, P.D., Stemhagen, A., Fontham, E.T., Bleecker, M.L., Stewart, P.A., & Hoover, R.N. (1987). Brain tumor mortality risk among men with electrical and electronics jobs: a case-control study. Journal of the National Cancer Institue, 79(2), 233-238. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/3474455 Tynes, T., Hannevik, M., Andersen, A., Vistnes, A.I, & Haldorsen, T. (1996). Valberg, P.A., van Deventer, T.E., & Repacholi, M.H. (2007). Workgroup Report: Base Stations and Wireless Networks Radiofrequency (RF) Exposures and Health Consequences. Environmental Health Perspectives, 115(3), 416-24; 85 University of Ghana http://ugspace.ug.edu.gh APPENDICES APPENDIX A: EM FIELDS EXPOSURE REFERENCE LEVELS Table A1 IEEE Maximum Permissible Exposures for occupational exposure (IEEE, 2006) Frequency RMS RMS RMS power Averaging range electric field magnetic density(S), E-field, H- time [E]2, strength[E]a field field (W/m) [H]2 or S (MHz) strength[H]a (V/m) (min) (A/m) 0.1-1.0 1842 16.3/f (9000,100000/f 2)b M M 6 1.0-30 1842/fM 16.3/fM (9000/f 2 M ,100000/f 2 M ) 6 30-100 61.4 16.3/f (10, 100000/f 2M M ) 6 100-300 61.4 0.163 10 6 300-3000 - - FM/20 6 3000-30000 - - 100 19.63/f 1.079 G 30000-300000 - - 100 2.524/f 0.476 G *NOTE 1. fM is the frequency in MHz, 2. fG is the frequency GHz 3. aFor exposures that are uniform over the dimensions of the body, such as certain far-field plane waves exposures the exposure field strengths and power densities are compared with MPE in the Table. For non-uniform exposures, the mean values of the exposure fields as obtained by spatially averaging the squares of the field strengths or averaging the power densities over an area equivalent to the vertical cross section of the human body(projected area), or a smaller area depending on the frequency, area compared with MPEs in the Table. 4. bThese plane-wave equivalent power density values are commonly used as a convenient comparison with MPE at higher frequencies and are displayed on some instruments. 86 University of Ghana http://ugspace.ug.edu.gh Table A2 IEEE Maximum Permissible Exposures for general public exposure (IEEE, 2006) Frequency RMS electric RMS power density(S), Averaging time [E]2, range field strength E-field, H-field [H]2 or S (MHz) [E]a(V/m) (W/m) (min) 0.1-1.34 614 (1000, 100000/) f 2M ) c 6 6 1.34-3 823.8/fM (1800/f 2 M ,100000/f 2 M ) f 2/0.3 M 6 3-30 823.8/fM (1800/f 2 M ,100000/f 2) f 2/0.3M M 6 30-100 27.5 (2, 9400 000/f 3.336M ) 30 6 100-400 27.5 2 30 6 400-2000 - fM/200 30 2000-5000 - 10 30 5000-30 000 10 150/fG 30 000-100 000 - 10 5048/f 0.476 G 100000-300 000 - (90fG-7000)/200 5048/[(9fG-7000)/ f 0.476G ] *NOTE 1. fM is the frequency in MHz, 2. fG is the frequency GHz 3. aFor exposures that are uniform over the dimensions of the body, such as certain far-field plane waves exposures the exposure field strengths and power densities are compared with MPE in the Table. For non-uniform exposures, the mean values of the exposure fields as obtained by spatially averaging the squares of the field strengths or averaging the power densities over an area equivalent to the vertical cross section of the human body(projected area), or a smaller area depending on the frequency, area compared with MPEs in the Table. 4. bThe left column is the averaging time for [E]2, the right column is the averaging time for [H]2. For frequencies greater than 400MHz, the averaging time is for power density 5. cThese plane-wave equivalent power density values are commonly used as a convenient comparison with MPE at higher frequencies and are displayed on some instruments 87 University of Ghana http://ugspace.ug.edu.gh Table A3 IEEE Maximum Permissible Exposure action levels from the main telecommunication Service Frequency Erms Srms Averaging range time [E]2, [H]2 (V/m) or S (MHz) (min) E field, H field VHF TV 54-88 27.50 2.00 6.27 30 6 FM broadcast 88-108 27.50 2.00 2.14 30 6 VHF TV 174-216 27.50 2.00 2.00 30 6 Trunking 800MHz 806-869 - 4.19 30 Mobile Telephony 824-894 - 4.30 30 800MHz Mobile Telephony 890-960 - 4.63 30 900MHz PCS 1800MHz 1710-1880 - 8.98 30 PCS 1900MHz 1850-1900 - 9.38 30 Table A4 FCC Limits for Maximum Permissible Exposure (MPE) for General Public (FCC, 1997) Frequency Electric Field Magnetic Field Power Density Averaging Range (MHz) S trength (E) Strength (H) (S) (mW/cm2) Time (V/m) (A/m) |E|2, |H|2 or S (minutes) 0.3-1.34 614 1.63 (100)* 30 1.34-30 824/f 2.19/f (180/f2)* 30 30-300 27.5 0.073 0.2 30 300-1500 -- -- f/1500 30 1500-100,000 -- -- 1.0 30 88 University of Ghana http://ugspace.ug.edu.gh NOTE 1. f is frequency in MHz. 2. *Plane-wave equivalent power density. Table A5 FCC Limits for Maximum Permissible Exposure (MPE) for Occupational (FCC, 1997) Frequency Electric Field Magnetic Field Power Density Averaging Range (MHz) S trength (E) Strength (H) (S) (mW/cm2) Time (V/m) (A/m) |E|2, |H|2 or S (minutes) 0.3-3.0 614 1.63 (100)* 6 3.0-30 1842/f 4.89/f (900/f2)* 6 30-300 61.4 0.163 1.0 6 300-1500 -- -- f/300 6 1500-100,000 -- -- 5 6 NOTE 1. f = frequency in MHz 2. *Plane-wave equivalent power density 3. Occupational/controlled limits apply in situations in which persons are exposed as a consequence of their employment provided those persons are fully aware of the potential for exposure and can exercise control over their exposure. 4. Limits for occupational/controlled exposure also apply in situations when an individual is transient through a location where occupational/controlled limits apply provided he or she is made aware of the potential for exposure. 89 University of Ghana http://ugspace.ug.edu.gh Table A6 ICNIRP reference levels (unperturbed rms values) (ICNIRP, 1998) Types of Frequency range E-field strength H-field Equivale exposure -1 strength nt plane (Vm ) wave (Am-1) power density S -eq(Wm 2) Up to 1Hz - 1.63 x 105 - 1-8Hz 20 000 1.63 x 105/f2 - 8-25Hz 20 000 2 x 104/f - 0.025-0.82kHz 500/f 20/f - Occupational 0.82-65kHz 610 24.4 - exposure 0.065-1MHz 610 1.6/f - 1-10MHz 610/f 1.6/f - 10-400MHZ 61 0.16 10 400-2000MHz 3 f 0.5 0.008/f 0.5 f /40 2-300GHz 137 0.36 50 Up to 1 Hz - 3.2 x 104 - 1-8 Hz 10 000 3.2 x 104/f2 - 8-25 Hz 10 000 4000/f - 0.025-0.8 kHz 250/f 4/f - 0.8-3 kHz 250/f 5 - General 3-150 kHz 87 5 - public 0.15-1 MHz 87 0.73/f - 1-10 MHZ 87/ f 0.5 0.73/f 2 10-400 MHZ 28 0.073 400-2000 MHz 1.375 f 0.5 0.0037f0.5 f /200 2-300 GHz 61 0.16 10 *NOTE 90 University of Ghana http://ugspace.ug.edu.gh 1. f as indicated in the frequency range column 2. For frequencies between 100 kHz and 10 GHz, the averaging time is 6 minutes. 3. For frequencies up to 100 kHz, the peak values can be obtained by multiplying the rms value by √2. For pulse of duration tp, the equivalent frequency to apply should be calculated as f =1/ (2tp). 4. Between 100 kHz and 10 MHz, peak values for the field strength are obtained by interpolation from the 1.5-fold peak at 100 MHz to the 32-fold peak at 10 MHz. for frequencies exceeding 10 MHz, it is suggested that the peak equivqlent plane-wave power density, as averaged over the pulse width, does not exceed 1000 times the Seq, limit or that the field strength does not exceed the field strength exposure levels given in the table. 5. For frequencies exceeding 10 GHz, the averaging time is 68/ f 1.05 minutes (f in GHz). Table A7 ICNIRP reference levels for general public exposure from the main telecommunications services and systems (WHO). Service Frequency E-field H-field B-field Equivalent range strength strength (µT) plane wave (MHz) (Vm-1) (Am-1) power density Seq (Wm-2) FM broadcast 88-108 28.0 0.073 0.092 2.0 VHF TV 54-88 28.0 0.073 0.0092 2.0 174-216 UHF TV 407-806 29.8 0.08 0.099 2.0 Trunking 800MHz 806-869 40.0 0.10 0.13 4.3 Mobile Telephony 824-894 40.6 0.11 0.14 4.4 800MHz Mobile Telephony 890-960 41.0 0.11 0.14 4.5 900MHz PCS 1800MHz 1710-1880 56.9 0.15 0.19 8.6 PCS 1900MHz 1850-1900 60.5 0.16 0.20 9.7 91 University of Ghana http://ugspace.ug.edu.gh Table A8 Typical sources of electromagnetic fields (Miller, 2002) Frequency range Frequencies Some examples of exposure sources Static 0 Hz VDU (video displays); MRI and other diagnostic /scientific instrumentation; Industrial electrolysis; ELF 0-300 Hz Power lines; Domestic distribution lines, Domestic appliances; Electric engines in cars, train; Welding devices IF 300 Hz – 3 kHz VDU; anti-theft devices in shops, hands free access control systems, card readers and metal detectors; MRI; Welding devices RF 3 kHz– 300 GHz Mobile telephony; Broadcasting and TV; Microwave oven; Radar, portable and stationary radio transceivers, personal mobile radio; MRI Table A9 Examples of emissions in the frequency band from 9 kHz TO 300 GHz (ECC, 2004) Symbols Frequency range (lower limit Services exclusive, upper limit inclusive VLF 9 to 30 kHz Induction heating LF 30 to 300 kHz Industrial induction heating, AM broadcasting, clock transmitters MF 300 to 3 000 kHz AM radio, industrial induction heating HF 3 to 30 MHz Broadcasting, Radio- amateurs, Armed Forces VHF 30 to 300 MHz PMR, TV, Armed Forces, Radio-amateurs, FM broadcasting, Aeronautical services UHF 300 MHz to 3 000 MHz TV, GSM, DCS, DECT, UMTS, Bluetooth, earth station, Radars 92 University of Ghana http://ugspace.ug.edu.gh SHF 3 to 30 GHz Radars, Earth stations, Microwave links EHF 30 to 300 GHz Radars, microwave links Table A10 Some quantities and SI-units used in the radiofrequency band (ICNIRP, 2009) QUANTITY SYMBOL SI-UNIT SYMBOL Conductivity Σ Siemens per meter S.m-1 Permittivity Ε Farad per meter F.m-1 Current I Ampere A Current density J Ampere per square A.m-2 meter Electric field strength E Volt per meter V.m-1 Power density S Watt per square meter W.m-2 Frequency F Hertz Hz Impedance Z Ohm Ω Magnetic field strength H ampere per kilogram A.kg-1 Propagation constant K Per meter m-1 Specific absorption SA Joule per kilogram J. kg-1 Specific absorption rate SAR Watt per kilogram W. kg-1 Wavelength Λ Meter M Magnetic flux density B Tesla T 93 University of Ghana http://ugspace.ug.edu.gh APENDIX B: MEASUREMENTS TABLES Table B1.01 Measured Power density levels (W/m2) surveyed at Vision One FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A1 05.72411°N, 19 4.89E-04 000.24941°W B1 05.72391°N, 61 6.63E-04 000.24896°W C1 05.72378°N, 94 1.22E-04 000.24867°W D1 05.72460°N, 96 8.29E-05 000.24891°W E1 05.72492°N, 111 1.31E-04 000.24916°W F1 05.72370°N, 129 6.45E-06 000.24838°W G1 05.72355°N, 162 5.80E-06 000.24811°W H1 05.72340°N, 203 5.47E-05 000.24777°W I1 05.72328°N, 232 3.42E-05 000.24756°W J1 05.72315°N, 252 3.91E-05 000.24739°W K1 05.72304°N, 272 2.28E-05 000.24724°W L1 05.72293°N, 290 4.49E-04 000.24711°W Table B1.02 Measured Power density levels (W/m2) surveyed at Marahaba FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A2 05.72492°N, 5 8.50E-04 000.24916°W B2 05.72460°N, 47 5.99E-04 000.24891°W 94 University of Ghana http://ugspace.ug.edu.gh C2 05.72411°N, 98 8.45E-06 000.24941°W D2 05.72391°N, 115 3.62E-04 000.24896°W E2 05.72378°N, 138 1.93E-04 000.24867°W F2 05.72370°N, 161 2.56E-04 000.24838°W G2 05.72355°N, 193 1.02E-04 000.24811°W H2 05.72340°N, 228 2.30E-06 000.24777°W I2 05.72328°N, 260 3.87E-06 000.24756°W J2 05.72315°N, 277 7.96E-05 000.24739°W K2 05.72304°N, 297 6.19E-06 000.24724°W L2 05.72293°N, 316 6.30E-05 000.24711°W Table B1.03 Measured Power density levels (W/m2) surveyed at Star FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A3 05.85826°N, 10 4.50E-03 000.16623°W B3 05.85826°N, 25 1.70E-04 000.16623°W C3 05.85826°N, 77 1.06E-04 000.16623°W D3 05.85826°N, 125 7.14E-06 000.16623°W E3 05.85826°N, 191 6.03E-06 000.16623°W F3 05.85826°N, 394 2.66E-05 000.16623°W 95 University of Ghana http://ugspace.ug.edu.gh G3 05.85826°N, 507 1.05E-05 000.16623°W H3 05.85826°N, 612 9.43E-08 000.16623°W I3 05.85826°N, 833 2.60E-08 000.16623°W J3 05.85826°N, 1,066 1.01E-08 000.16623°W K3 05.85826°N, 1,249 1.41E-07 000.16623°W L3 05.85826°N, 1,468 2.00E-07 000.16623°W Table B1.04 Measured Power density levels (W/m2) surveyed at Star FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A4 05.85826°N, 10 1.61E-02 000.16623°W B4 05.85843°N, 25 5.08E-07 000.16638°W C4 05.85847°N, 77 3.60E-05 000.16686°W D4 05.85818°N, 125 4.67E-05 000.16730°W E4 05.85767°N, 191 1.33E-04 000.16777°W F4 05.85602°N, 394 3.00E-05 000.16887°W G4 05.85497°N, 507 5.80E-06 000.16923°W H4 05.85412°N, 612 3.26E-07 000.16971°W I4 05.85266°N, 833 4.20E-08 000.17110°W J4 05.85070°N, 1,066 4.72E-08 000.17204°W 96 University of Ghana http://ugspace.ug.edu.gh K4 05.84901°N, 1,249 6.54E-07 000.17246°W L4 05.84699°N, 1,468 1.94E-07 000.17296°W Table B1.05 Measured Power density levels (W/m2) surveyed at Live FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A5 05.85826°N, 10 1.41E-02 000.16623°W B5 05.85843°N, 25 1.78E-03 000.16638°W C5 05.85847°N, 77 3.55E-05 000.16686°W D5 05.85818°N, 125 1.27E-04 000.16730°W E5 05.85767°N, 191 4.42E-05 000.16777°W F5 05.85602°N, 394 3.26E-06 000.16887°W G5 05.85497°N, 507 6.35E-07 000.16923°W H5 05.85412°N, 612 1.54E-06 000.16971°W I5 05.85266°N, 833 3.46E-08 000.17110°W J5 05.85070°N, 1,066 5.33E-07 000.17204°W K5 05.84901°N, 1,249 2.85E-07 000.17246°W L5 05.84699°N, 1,468 3.14E-08 000.17296°W Table B1.06 Measured Power density levels (W/m2) surveyed at Oman FM 97 University of Ghana http://ugspace.ug.edu.gh TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A6 05.85843°N, 11 2.98E-04 000.16638°W B6 05.85826°N, 33 6.09E-05 000.16623°W C6 05.85847°N, 54 1.61E-05 000.16686°W D6 05.85818°N, 110 1.14E-05 000.16730°W E6 05.85767°N, 182 1.30E-05 000.16777°W F6 05.85602°N, 393 2.04E-05 000.16887°W G6 05.85497°N, 508 3.93E-05 000.16923°W H6 05.85412°N, 614 7.44E-08 000.16971°W I6 05.85266°N, 835 1.78E-08 000.17110°W J6 05.85070°N, 1,071 8.23E-07 000.17204°W K6 05.84901°N, 1,250 8.58E-07 000.17246°W L6 05.84699°N, 1,477 2.30E-07 000.17296°W Table B1.07 Measured Power density levels (W/m2) surveyed at Happy FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A7 05.85843°N, 11 1.20E-03 000.16638°W B7 05.85826°N, 33 2.05E-04 000.16623°W 98 University of Ghana http://ugspace.ug.edu.gh C7 05.85847°N, 54 1.43E-04 000.16686°W D7 05.85818°N, 110 1.62E-05 000.16730°W E7 05.85767°N, 182 2.04E-05 000.16777°W F7 05.85602°N, 393 1.34E-05 000.16887°W G7 05.85497°N, 508 1.18E-05 000.16923°W H7 05.85412°N, 614 4.07E-07 000.16971°W I7 05.85266°N, 835 6.41E-07 000.17110°W J7 05.85070°N, 1,071 1.60E-07 000.17204°W K7 05.84901°N, 1,250 2.78E-07 000.17246°W L7 05.84699°N, 1,477 1.20E-07 000.17296°W Table B1.08 Measured Power density levels (W/m2) surveyed at Y- FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A8 05.85843°N, 11 1.66E-04 000.16638°W B8 05.85826°N, 33 6.05E-05 000.16623°W C8 05.85847°N, 54 2.70E-06 000.16686°W D8 05.85818°N, 110 3.32E-06 000.16730°W E8 05.85767°N, 182 4.77E-05 000.16777°W F8 05.85602°N, 393 7.41E-05 000.16887°W 99 University of Ghana http://ugspace.ug.edu.gh G8 05.85497°N, 508 3.75E-05 000.16923°W H8 05.85412°N, 614 1.94E-07 000.16971°W I8 05.85266°N, 835 6.47E-07 000.17110°W J8 05.85070°N, 1,071 5.72E-07 000.17204°W K8 05.84901°N, 1,250 3.83E-07 000.17246°W L8 05.84699°N, 1,477 7.01E-07 000.17296°W Table B1.09 Measured Power density levels (W/m2) surveyed at Joy FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A9 05.85826°N, 82 2.49E-04 000.16623°W B9 05.85843°N, 114 1.63E-04 000.16638°W C9 05.85847°N, 152 2.76E-06 000.16686°W D9 05.85818°N, 173 4.53E-05 000.16730°W E9 05.85767°N, 212 5.54E-07 000.16777°W F9 05.85602°N, 373 3.42E-07 000.16887°W G9 05.85497°N, 474 1.67E-06 000.16923°W H9 05.85412°N, 578 4.41E-06 000.16971°W I9 05.85266°N, 796 1.21E-06 000.17110°W J9 05.85070°N, 1024 8.23E-07 000.17204°W K9 05.84901°N, 1197 1.14E-06 000.17246°W 100 University of Ghana http://ugspace.ug.edu.gh L9 05.84699°N, 1407 1.70E-07 000.17296°W Table B1.10 Measured Power density levels (W/m2) surveyed at Asempa FM POSITION CORDINATES DISTANCE POWER DENSITY FROM (W/m2) ANTENNA (METERS) A10 05.85826°N, 82 3.05E-05 000.16623°W B10 05.85843°N, 114 6.80E-06 000.16638°W C10 05.85847°N, 152 8.29E-05 000.16686°W D10 05.85818°N, 173 7.11E-06 000.16730°W E10 05.85767°N, 212 5.22E-07 000.16777°W F10 05.85602°N, 373 1.56E-06 000.16887°W G10 05.85497°N, 474 7.17E-08 000.16923°W H10 05.85412°N, 578 1.55E-07 000.16971°W I10 05.85266°N, 796 1.25E-08 000.17110°W J10 05.85070°N, 1024 1.22E-08 000.17204°W K10 05.84901°N, 1197 9.33E-08 000.17246°W L10 05.84699°N, 1407 2.49E-08 000.17296°W Table B2.01 FM model Power density levels (W/m2) surveyed at Vision One FM 101 University of Ghana http://ugspace.ug.edu.gh TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A1 05.72411°N, 19 3.06E-01 000.24941°W B1 05.72391°N, 61 7.84E-02 000.24896°W C1 05.72378°N, 94 2.41E-2 000.24867°W D1 05.72460°N, 96 6.46E-04 000.24891°W E1 05.72492°N, 111 8.33E-05 000.24916°W F1 05.72370°N, 129 1.35E-03 000.24838°W G1 05.72355°N, 162 1.02E-02 000.24811°W H1 05.72340°N, 203 8.78E-03 000.24777°W I1 05.72328°N, 232 9.11E-03 000.24756°W J1 05.72315°N, 252 1.18E-04 000.24739°W K1 05.72304°N, 272 7.90E-03 000.24724°W L1 05.72293°N, 290 1.40E-02 000.24711°W Table B2.02 FM model Power density levels (W/m2) surveyed at Marahaba FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A2 05.72492°N, 5 7.42E-01 000.24916°W B2 05.72460°N, 47 6.19E-02 000.24891°W 102 University of Ghana http://ugspace.ug.edu.gh C2 05.72411°N, 98 2.74E-02 000.24941°W D2 05.72391°N, 115 7.44E-02 000.24896°W E2 05.72378°N, 138 1.18E-01 000.24867°W F2 05.72370°N, 161 2.23E-02 000.24838°W G2 05.72355°N, 193 5.64E-05 000.24811°W H2 05.72340°N, 228 4.35E-02 000.24777°W I2 05.72328°N, 260 6.23E-03 000.24756°W J2 05.72315°N, 277 3.24E-02 000.24739°W K2 05.72304°N, 297 4.00E-02 000.24724°W L2 05.72293°N, 316 1.76E-02 000.24711°W Table B2.03 FM model Power density levels (W/m2) surveyed at Star FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A3 05.85826°N, 10 3.13E+00 000.16623°W B3 05.85826°N, 25 2.68E+00 000.16623°W C3 05.85826°N, 77 3.81E-01 000.16623°W D3 05.85826°N, 125 1.78E-01 000.16623°W E3 05.85826°N, 191 1.58E-03 000.16623°W F3 05.85826°N, 394 2.29E-02 000.16623°W 103 University of Ghana http://ugspace.ug.edu.gh G3 05.85826°N, 507 1.13E-02 000.16623°W H3 05.85826°N, 612 4.37E-04 000.16623°W I3 05.85826°N, 833 1.10E-02 000.16623°W J3 05.85826°N, 1,066 4.64E-03 000.16623°W K3 05.85826°N, 1,249 1.41E-03 000.16623°W L3 05.85826°N, 1,468 2.43E-4 000.16623°W Table B2.04 FM model Power density levels (W/m2) surveyed at Star FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A4 05.85826°N, 10 9.72E-01 000.16623°W B4 05.85843°N, 25 9.06E-01 000.16638°W C4 05.85847°N, 77 2.65E-02 000.16686°W D4 05.85818°N, 125 1.18E-02 000.16730°W E4 05.85767°N, 191 1.31E-01 000.16777°W F4 05.85602°N, 394 4.10E-02 000.16887°W G4 05.85497°N, 507 9.12E-03 000.16923°W H4 05.85412°N, 612 1.59E-02 000.16971°W I4 05.85266°N, 833 8.15E-04 000.17110°W J4 05.85070°N, 1,066 5.73E-03 000.17204°W 104 University of Ghana http://ugspace.ug.edu.gh K4 05.84901°N, 1,249 4.29E-03 000.17246°W L4 05.84699°N, 1,468 1.74E-03 000.17296°W Table B2.05 FM model Power density levels (W/m2) surveyed at Live FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A5 05.85826°N, 10 1.02E+00 000.16623°W B5 05.85843°N, 25 8.19E-01 000.16638°W C5 05.85847°N, 77 8.57E-02 000.16686°W D5 05.85818°N, 125 2.28E-02 000.16730°W E5 05.85767°N, 191 3.72E-04 000.16777°W F5 05.85602°N, 394 3.88E-03 000.16887°W G5 05.85497°N, 507 1.03E-03 000.16923°W H5 05.85412°N, 612 3.95E-03 000.16971°W I5 05.85266°N, 833 1.62E-03 000.17110°W J5 05.85070°N, 1,066 1.98E-0-4 000.17204°W K5 05.84901°N, 1,249 1.59E-05 000.17246°W L5 05.84699°N, 1,468 5.99E-06 000.17296°W Table B2.06 FM model Power density levels (W/m2) surveyed at Oman FM 105 University of Ghana http://ugspace.ug.edu.gh TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A6 05.85843°N, 11 2.09E+00 000.16638°W B6 05.85826°N, 33 4.63E-02 000.16623°W C6 05.85847°N, 54 0.4.80E-01 000.16686°W D6 05.85818°N, 110 1.63E-01 000.16730°W E6 05.85767°N, 182 9.15E-02 000.16777°W F6 05.85602°N, 393 2.64E-04 000.16887°W G6 05.85497°N, 508 2.23E-02 000.16923°W H6 05.85412°N, 614 7.60E-04 000.16971°W I6 05.85266°N, 835 6.16E-03 000.17110°W J6 05.85070°N, 1,071 5.01E-03 000.17204°W K6 05.84901°N, 1,250 2.03E-03 000.17246°W L6 05.84699°N, 1,477 4.78E-05 000.17296°W Table B2.07 FM model Power density levels (W/m2) surveyed at Happy FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A7 05.85843°N, 11 2.90E-01 000.16638°W 106 University of Ghana http://ugspace.ug.edu.gh B7 05.85826°N, 33 1.87E-01 000.16623°W C7 05.85847°N, 54 4.21E-01 000.16686°W D7 05.85818°N, 110 1.61E-01 000.16730°W E7 05.85767°N, 182 1.41E-02 000.16777°W F7 05.85602°N, 393 4.23E-03 000.16887°W G7 05.85497°N, 508 9.43E-03 000.16923°W H7 05.85412°N, 614 2.50E-03 000.16971°W I7 05.85266°N, 835 1.26E-03 000.17110°W J7 05.85070°N, 1,071 2.42E-03 000.17204°W K7 05.84901°N, 1,250 1.30E-03 000.17246°W L7 05.84699°N, 1,477 3.97E-04 000.17296°W Table B2.08 FM Power model density levels (W/m2) surveyed at Y- FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A8 05.85843°N, 11 2.32E-04 000.16638°W B8 05.85826°N, 33 7.070E-02 000.16623°W C8 05.85847°N, 54 3.19E-02 000.16686°W D8 05.85818°N, 110 3.62E-04 000.16730°W E8 05.85767°N, 182 8.89E-03 000.16777°W 107 University of Ghana http://ugspace.ug.edu.gh F8 05.85602°N, 393 2.37E-03 000.16887°W G8 05.85497°N, 508 5.33E-04 000.16923°W H8 05.85412°N, 614 8.72E-04 000.16971°W I8 05.85266°N, 835 4.86E-05 000.17110°W J8 05.85070°N, 1,071 2.42E-03 000.17204°W K8 05.84901°N, 1,250 1.31E-03 000.17246°W L8 05.84699°N, 1,477 3.97E-04 000.17296°W Table B2.09 FM model Power density levels (W/m2) surveyed at Joy FM TEST CORDINATES DISTANCE POWER DENSITY POINTS FROM (W/m2) ANTENNA (METERS) A9 05.85826°N, 82 3.09E-03 000.16623°W B9 05.85843°N, 114 5.42E-02 000.16638°W C9 05.85847°N, 152 4.12E-02 000.16686°W D9 05.85818°N, 173 5.59E-02 000.16730°W E9 05.85767°N, 212 3.95E-02 000.16777°W F9 05.85602°N, 373 1.11E-02 000.16887°W G9 05.85497°N, 474 2.64E-03 000.16923°W H9 05.85412°N, 578 4.46E-03 000.16971°W I9 05.85266°N, 796 3.65E-04 000.17110°W 108 University of Ghana http://ugspace.ug.edu.gh J9 05.85070°N, 1024 1.74E-03 000.17204°W K9 05.84901°N, 1197 1.17E-03 000.17246°W L9 05.84699°N, 1407 4.45E-04 000.17296°W Table B2.10 FM model Power density levels (W/m2) surveyed at Asempa FM POSITION CORDINATES DISTANCE POWER DENSITY FROM (W/m2) ANTENNA (METERS) A10 05.85826°N, 82 3.09E-03 000.16623°W B10 05.85843°N, 114 5.42E-02 000.16638°W C10 05.85847°N, 152 4.12E-02 000.16686°W D10 05.85818°N, 173 5.59E-02 000.16730°W E10 05.85767°N, 212 3.95E-02 000.16777°W F10 05.85602°N, 373 1.11E-02 000.16887°W G10 05.85497°N, 474 2.64E-03 000.16923°W H10 05.85412°N, 578 4.46E-03 000.16971°W I10 05.85266°N, 796 3.65E-04 000.17110°W J10 05.85070°N, 1024 1.74E-03 000.17204°W K10 05.84901°N, 1197 1.17E-03 000.17246°W L10 05.84699°N, 1407 4.45E-04 000.17296°W Table B3 Electric field spatial average strength for various FM stations 109 University of Ghana http://ugspace.ug.edu.gh FM station Latitude Longitude Electric Field (V/m) VISION ONE 05° 38' 22.8'' N 0°14' 33.6'' W 2.57E-01 ± 1.54E-01 FM MARAHABA 05° 43' 29.8''N 000° 14' 56.9"W 2.82E-01 ± 1.79E-01 FM STAR FM 05° 51' 30.8" N 00° 09' 59.0'' W 3.90E-01 ± 3.66E-01 KASAPA FM 05° 51' 30.8''N 000° 09' 59.0"W 7.17E-01 ± 6.97E-01 LIVE FM 05°36' 22.1''N 000°13' 34.1''W 7.11E-01 ± 6.70E-01 OMAN FM 05° 51' 30.5'' N 00° 10' 00.4'' W 1.20E-01 ± 9.37E-02 HAPPY FM 05° 51' 30.5'' N 000° 10' 58.8'' W 2.25E-01 ± 1.93E-01 ASEMPA FM 05° 51' 32.6'' N 000° 10' 00.4" W 6.39E-02 ± 5.39E-02 JOY FM 05° 51' 43'' N 000° 09' 50" W 1.22E-01 ± 1.01E-01 Y-FM 05° 51' 30.5'' N 00° 10' 00.4'' W 1.11E-01 ± 8.12E-02 110 University of Ghana http://ugspace.ug.edu.gh APENDIX C TECHNICAL PARAMETERS FOR THE FM ANTENNAS TRADE ASSIGNED ANTENNA ANTENNA POWER EFFECTIVE NAME FREQUENCY MOUNTIN GAIN (dB) TO ISOTROPIC (MHz) G HEIGHT ANTENNA RADIATED (M) (W) POWER (EIRP) (W) STAR FM 103.5 50 9 5000 39716.41 ASEMPA 94.7 50 10 4300 43000 FM HAPPY 98.9 60 7.2 2600 13644.99 FM Y-FM 107.9 65 3.5 900 2014.849 JOY FM 99.7 61 4.3 4430 9420.372 OMAN 107.1 55 9 4000 31773.13 FM VISION 93.5 50 6 1500 5971.608 ONE LIVE FM 91.9 39 11.7 600 8874.65 KASAPA 102.3 65 9.5 4000 35650.04 FM MARAHA 99.3 50 7.2 3500 18368.26 BA FM 111 University of Ghana http://ugspace.ug.edu.gh APPENDIX D COMPARATIVE GRAPHS FOR MEASURED AND CALCULATED POWER DENSITY LEVELS OF FM STATIONS VISION ONE 93.5MHz FM 3.50E-03 3.00E-03 2.50E-03 2.00E-03 1.50E-03 1.00E-03 5.00E-04 0.00E+00 0 50 100 150 200 250 300 350 -5.00E-04 DISTANCE FROM TOWER (m) Real Time Measurement(W/m^2) Numerical Predictive Model (mW/m^2) STAR 103.5MHz FM 3.50E-02 3.00E-02 2.50E-02 2.00E-02 1.50E-02 1.00E-02 5.00E-03 0.00E+00 0 200 400 600 800 1000 1200 1400 1600 -5.00E-03 DISTANCE FROM TOWER (m) Real Time Measurement(W/m^2) Numerical Predictive Model (mW/m^2) 112 POWER DENSITY POWER DENSITY University of Ghana http://ugspace.ug.edu.gh KASAPA 102.3MHz FM 1.80E-02 1.60E-02 1.40E-02 1.20E-02 1.00E-02 8.00E-03 6.00E-03 4.00E-03 2.00E-03 0.00E+00 0 200 400 600 800 1000 1200 1400 1600 -2.00E-03 -4.00E-03 DISTANCE FROM TOWER (m) Real Time Measurement(W/m^2) Numerical Predictive Model (mW/m^2) LIVE 91.9MHz FM 1.60E-02 1.40E-02 1.20E-02 1.00E-02 8.00E-03 6.00E-03 4.00E-03 2.00E-03 0.00E+00 0 200 400 600 800 1000 1200 1400 1600 -2.00E-03 DISTANCE FROM TOWER (m) Real Time Measurement(W/m^2) Numerical Predictive Model (mW/m^2) 113 POWER DENSITY POWER DENSITY University of Ghana http://ugspace.ug.edu.gh OMAN 107.1MHZ FM 2.50E-02 2.00E-02 1.50E-02 1.00E-02 5.00E-03 0.00E+00 0 200 400 600 800 1000 1200 1400 1600 -5.00E-03 DISTANCE FROM TOWER (m) Real Time Measurement(W/m^2) Numerical Predictive Model (mW/m^2) HAPPY 98.9MHz FM 4.50E-03 4.00E-03 3.50E-03 3.00E-03 2.50E-03 2.00E-03 1.50E-03 1.00E-03 5.00E-04 0.00E+00 0 200 400 600 800 1000 1200 1400 1600 -5.00E-04 DISTANCE FROM TOWER (m) Real Time Measurement(W/m^2) Numerical Predictive Model (mW/m^2) 114 POWER DENSITY POWER DENSITY University of Ghana http://ugspace.ug.edu.gh Y - FM(107.9MHz) 8.00E-04 7.00E-04 6.00E-04 5.00E-04 4.00E-04 3.00E-04 2.00E-04 1.00E-04 0.00E+00 0 200 400 600 800 1000 1200 1400 1600 -1.00E-04 DISTANCE FROM TOWER (m) Real Time Measurement(W/m^2) Numerical Predictive Model (mW/m^2) JOY 99.7MHZ FM 6.00E-04 5.00E-04 4.00E-04 3.00E-04 2.00E-04 1.00E-04 0.00E+00 0 200 400 600 800 1000 1200 1400 1600 -1.00E-04 DISTANCE FROM TOWER (m) Real Time Measurement(W/m^2) Numerical Predictive Model (mW/m^2) 115 POWER DENSITY POWER DENSITY University of Ghana http://ugspace.ug.edu.gh ASEMPA 94.7MHz FM 4.00E-03 3.50E-03 3.00E-03 2.50E-03 2.00E-03 1.50E-03 1.00E-03 5.00E-04 0.00E+00 0 200 400 600 800 1000 1200 1400 1600 -5.00E-04 DISTANCE FROM TOWER (m) Real Time Measurement(W/m^2) Numerical Predictive Model (mW/m^2) 116 POWER DENSITY University of Ghana http://ugspace.ug.edu.gh APPENDIX E SSPECTRUM ANALYZER DATA Figure E2: Spectrum location ‘B2’ for Marahaba 99.3MHz FM Figure E3: Spectrum location ‘C2’ for Marahaba 99.3MHz FM 117 University of Ghana http://ugspace.ug.edu.gh Figure E4: Spectrum location ‘D2’ for Marahaba 99.3MHz FM Figure E5: Spectrum location ‘E2’ for Marahaba 99.3MHz FM 118 University of Ghana http://ugspace.ug.edu.gh Figure E6: Spectrum location ‘F2’ for Marahaba 99.3MHz FM Figure E7: Spectrum location ‘G2’ for Marahaba 99.3MHz FM 119 University of Ghana http://ugspace.ug.edu.gh Figure E8: Spectrum location ‘H2’ for Marahaba 99.3MHz FM Figure E9: Spectrum location ‘I2’ for Marahaba 99.3MHz FM 120 University of Ghana http://ugspace.ug.edu.gh Figure E10: Spectrum location ‘J2’ for Marahaba 99.3MHz FM Figure E11: Spectrum location ‘K2’ for Marahaba 99.3MHz FM 121 University of Ghana http://ugspace.ug.edu.gh Figure E12: Spectrum location ‘L2’ for Marahaba 99.3MHz FM 122