Evaluation And Analysis Of Electromagnetic Field Strength Of Nta Signal In Port Harcourt And Its Environs

ABSTRACT

This project work is on analysis of Electromagnetic Field Strength of NTA Port  Harcourt, which operate at a frequency of: 210.25 MHz-Vision, 215.75MHz-Audio
Channel: 10VHF, in Port Harcourt and its environs with the aid of an automated Band scanner GPS system. The measurements were carried out by taking the television station’s transmitter as a reference point at the center and selecting 24 measuring point around the transmitter. The Received Signal Strength (RSSS) due to the TV Transmitter were measured at the selected measuring points and the Result obtained was critically analyzed and interpreted with the aid of an attenuation decay curve. NTA Port Harcourt Signal was able to travel the distance stated in this paper because of the ground constant of the terrain, reflection of signal from the earth surface, Diffraction by Obstacles and the transmitter parameters (transmitter power, Antenna height and antenna Gain).The signal strength diminishes fairly with distance from the source of electromagnetic waves

CHAPTER ONE

1.0                                 BACKGROUND OF THE STUDY

1.1                                            INTRODUCTION

The quantitative measure of the strength of an electric field is known as the electric field strength (intensity) measurement. From electrostatics studies, we can loosely define electric field strength at a point as the force on a unit positive charge at that point and is measured in Newtons per coulomb or volt per meter (Vm^– 1). A radio wave is an electromagnetic wave which emanates from a radiating source, the radio wave assumes all the properties of a plane wave. The wave-front is the plane which contain the electric (E) and magnetic (H) vectors and is at right angles to the direction of propagation and power flow. Usually, it is convenient to carry out studies in terms of the electric component, E of the wave which is known as the electric field strength of the wave. [1]

This work present the evaluation and analysis of the measured and calculated Electromagnetic field strength of NTA station at 24 different locations, That is, six locations due EAST, NORTH, WEST and SOUTH of the Radio Transmitter respectively with 1Km interval as shown in figure 1 below using an automated mobile Band Scanner GPS system.

NTA  station is located at  Choba Road, Mgbuoba (latitude: 4°51’48.52″N, longitude: 6°57’48.80″E) transmits at a Frequency: 210.25 MHz-Vision, 215.75MHz-Audio Channel: 10VHF. The radio signal is propagated using space wave propagation mode.  The measurement of electromagnetic field strength of NTA Port Harcourt is signals at different locations, that is, locations due EAST, NORTH, WEST and SOUTH of the Transmitter respectively with 1Km interval was obtained using an automated mobile Band Scanner GPS system.

Band Scanner GPS is a tool used to evaluate television broadcast band and to log station identification parameters such as electromagnetic field strength, bandwidth, received power at a distance and radio data system strength. “Band Scanner GPS” is a Google Earth compatible tool for visualization of selected TV measurements. When running any campaign with the “Band Scanner GPS”, results will be saved in a Log file. “Band Scanner GPS” can then convert this file into KMZ format and view the results in Google Earth. The Log file can be exported also as transitional format for future analysis or to keep it in record. The “Band Scanner GPS” can measure signan level, MPX deviation, Left and Right visual levels, Pilot injection levels and RDS. The system is powered by the USB port of any Windows PC. [2]The result of the measurement is used to plot the attenuation decay graph of the station’s transmitting antenna.

The transmitter uses a Yagi-Uda antenna mounted on a mask that is 67feet (20.4 meter) high. The Output of the STL receiver is connected to the station’s main transmitter and the received signal is then re-transmitted with aid of a circularly Polarized antenna to the end user of the signal.

Transmitting television antennas are usually constructed as a system of horizontal, symmetrical dipoles; the feed arrangements and circuitry for the dipoles determine the shape of the polarization pattern and the antenna gain. The radiation pattern of transmitting antennas is usually circular in the horizontal plane; in the vertical plane it is lobe-shaped and directed along the earth’s surface. If the cross-sectional dimensions of the antenna mounting are relatively small and only a few units of antenna gain are needed, a turnstile antenna may be used in the VHF band. In other cases, it is preferable to use an antenna composed of separate panels, each consisting of dipoles and several auxiliary elements. Depending on the radiation pattern desired, the panels may be arranged symmetrically or nonsymmetrically with respect to the cross-sectional configuration of the mounting, and the radio waves radiated may either be in phase or have specific phase shifts.

1.2                                  PROBLEM STATEMENT

Electromagnetic fields (EMF) have been implicated to influence a range of bodily functions. Given their ubiquitous nature, widespread applications, and capability to produce deleterious effects, conclusive investigations of the health risks are critical. Accordingly, this paper has been constructed to weigh the bioeffects, possible biointeraction mechanisms, and research areas in bioelectromagnetics seeking immediate attention.

1.3                                       AIM OF THE STUDY

The main aim of this study is to measure electromagnetic field strength of NTA station on Port Harcourt can be measured and to analyse how its electromagnetic field radiation affects its environment.

1.4                            SIGNIFICANCE OF THE STUDY

It is important to carry out studies in terms of the electric component, E of the wave which is known as the electric field strength of the wave. The quantitative measure of the strength of an Electric field is known as the Electric field strength measurement. From Electrostatics studies, we  can loosely define Electric field strength at a point as the force on a unit positive charge at that point and is measured in Newton’s per Coulomb or Volts per meter (Vm-1). The level of Electromagnetic field strength needed to provide adequate reception in the presence of an interfering signal(s) is referred to as the usable field strength.

1.5                                    SCOPE OF THE STUDY

A radio wave is an Electromagnetic wave which emanates from a radiating source. The radio wave assumes all the properties of a plane wave; the wave-front is the plane which contains the Electric (E) and Magnetic (H) vectors and is at right angle to the direction of propagation and power flow. This work presents values and analysis of the measured Electromagnetic field strength of NTA station at different locations, that is, locations due EAST, NORTH, WEST and SOUTH of the television Transmitter respectively with 1Km interval between two measuring points using an automated mobile Band Scanner GPS system.

1.6                                               RESEARCH HYPOTHESIS

Ho: electromagnetic field has no negative effect on human health

H1: electromagnetic field has much negative effect on human health.

• RESEARCH QUESTION

The research questions are also follows:

1. What effects has electromagnetic field on human health?
2. What measures can be used to protect human health from electromagnetic field?

• To what extent does NTA electromagnetic field affect the environ?

1. Is NTA antenna or mast one of the causes of electromagnetic field?

1.8                                             TERMS AND DEFINITIONS

This section includes technical terms and definitions used within the document. The definitions are given in alphabetical order.

Conductivity: A property of materials that determines the magnitude of the electric current density when an electric field is impressed on the material.

Dielectric properties: In the context of this document the properties of materials conductivity and permeability.

Electric field strength (E): The magnitude of a field vector at a point that represents the force (F) on a charge (q). E is defined as E = F/q and is expressed in units of Volt per meter (V/m).

Electromagnetic field: Electromagnetic phenomena expressed in vector functions of space and time.

Electromagnetic radiation: The propagation of energy in the form of electromagnetic waves through space.

EMF: Electromagnetic field.

Exposure: Exposure occurs wherever a person is subjected to electric, magnetic or electromagnetic fields or contact currents other than those originating from physiological processes in the body.

Extremely low frequency (ELF): Extremely low frequency fields include, in this document, electromagnetic fields from 1 to 300 Hz.

Frequency modulation (FM): Frequency Modulation is a type of modulation representing information as variations in the frequency of a carrier wave. FM is often used at VHF frequencies (30 to 300 MHz) for broadcasting music and speech.

Frequency (Hz): The number of cycles of a repetitive waveform per second.

Intermediate frequencies (IF): Intermediate frequencies are, in the frame of this report, defined as frequencies between 300 Hz and 100 kHz.

Magnetic flux density (B): the magnitude of a field vector at a point that results in a force (F) on a charge (q) moving with the velocity (v). The force F is defined by F = q*(v x B) and is expressed in units of Tesla (T).

Magnetic field strength (H): the magnitude of a field vector that is equal to the magnetic flux density (B) divided by the permeability (µ) of the medium. H is defined as H = B/µ and is expressed in units of Ampere per metre (A/m).

Microwaves: Microwaves are defined in the frame of this expertise as electromagnetic waves with wavelengths of approximately 30 cm (1 GHz) to 1 mm (300 GHz).

Milliwatt (mW): A unit of power equal to 10^-3 Watt.

Nanowatt (nW): A unit of power equal to 10^-9 Watt.

Non – thermal effects (or athermal effects): An effect which can only be explained in terms of mechanisms other than increased molecular motion (i.e. heating), or occurs at absorbed power levels so low, that a thermal mechanism seems unlikely, or displays so unexpected a dependence upon some experimental variable that it is difficult to see how heating could be the cause.

Permeability: A property of materials that indicates how much polarisation occurs when an electric field is applied.

Power density (S): Power per unit area normal to the direction of propagation, usually  expressed in watts per meter squared (W/m²).

Radio frequency (RF): The frequencies between 100 kHz and 300 GHz of the electromagnetic spectrum.

Specific absorption rate (SAR): A measure of the rate of power absorbed by or dissipated in an incremental mass contained in a volume element of dielectric materials such as biological tissues. SAR is usually expressed in terms of watts per kilogram (W/kg).

Static electric field: Static fields produced by fixed potential differences.

Static magnetic fields: Static fields established by permanent magnets and by steady currents.