Design And Construction Of A 92.5MHz FM Transmitter

An FM transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves.

FM transmitter is basically a VHF colipits oscillator capable of transmitting sound or music to any standard FM receiver. The circuit works on a D.C source which makes it for a pure rectification. FM transmitter also has a capacitor microphone which picks up very weak sound signals.

The FM transmitter was designed using transistors and other component such resistor, inductor and capacitors. This project transmits frequency on 92.5MHz± 5%. The transmitting distance is l00metres. It is powered with 5volt – 15volts D.C battery using suitable F.M receiver tuned to the transmitting frequency of this project. F.M Transmitter can be used as cordless microphones, mobile phone and for public address purposes. The distant of transmission is limited to 100m and fixed frequency of transmission, away from all other radio station. This gives best range and least interference.

TABLE OF CONTENTS

TABLE OF CONTENT

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

CHAPTER ONE

1.0      INTRODUCTION

1.1      BACKGROUND OF THE PROJECT

1.2      PROBLEM STATEMENT

1.3      PURPOSE OF THE PROJECT

1.4      OBJECTIVE OF THE PROJECT

1.5      LIMITATIONS OF THE PROJECT

1.6      SCOPE OF THE PROJECT

1.7      APPLICATION OF THE PROJECT

1.8      DEFINITION OF TERMS

1.9      METHODOLOGY

1.10   PROJECT ORGANISATION

CHAPTER TWO

2.0 LITERATURE REVIEW

2.1 HISTORITICAL BACKGROUND OF THE PROJECT

2.2 REVIEW OF PARTS OF RADIO TRANSMITTER

2.3 REVIEW OF FM BROADCAST BANDS

2.4 MODULATION AND DEMODULATION

2.5 PRE-EMPHASIS AND DE-EMPHASIS

2.6 REVIEW OF MODULATION CHARACTERISTICS

CHAPTER THREE

3.0 CONSTRUCTION

3.1 BASICS OF FM TRANSMITTER

3.2 BLOCK DIAGRAM OF AN FM TRANSMITTER

3.3 FUNCTION OF FM TRANSMITTER BLOCK

3.4 CIRCUIT DIAGRAM OF THE SYSTEM

3.5 CIRCUIT PARTS

3.6 CIRCUIT OPERATION

3.7 DESCRIPTION OF COMPONENTS USED

CHAPTER FOUR

4.0 RESULT ANALYSIS

4.1 CONSTRUCTION PROCEDURE AND TESTING

4.2 CASING AND PACKAGING

4.3 ASSEMBLING OF SECTIONS

4.4 TESTING OF SYSTEM OPERATION

4.5 INSTALLATION OF THE COMPLETED DESIGN

4.6 SYSTEM TROUBLESHOOTING METHOD

4.7 COST ANALYSIS

CHAPTER FIVE

5.0 CONCLUSION

5.1 RECOMMENDATION

5.2 BIBLIOGRAPHY

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                         BACKGROUND OF THE PROJECT

In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves. In addition to their use in broadcasting, transmitters are necessary component parts of many electronic devices that communicate by radio, such as cell phones, wireless computer networks, Bluetooth enabled devices, garage door openers, two-way radios in aircraft, ships, and spacecraft, radar sets, and navigational beacons. The term transmitter is usually limited to equipment that generates radio waves for communication purposes; or radiolocation, such as radar and navigational transmitters. Generators of radio waves for heating or industrial purposes, such as microwave ovens or diathermy equipment, are not usually called transmitters even though they often have similar circuits.

The term is popularly used more specifically to refer to a broadcast transmitter, a transmitter used in broadcasting, as in FM radio transmitter. This usage usually includes the transmitter proper, the antenna, and often the building it is housed in.

A transmitter can be a separate piece of electronic equipment, or an electrical circuit within another electronic device. A transmitter and receiver combined in one unit is called a transceiver. The term transmitter is often abbreviated “XMTR” or “TX” in technical documents. The purpose of most transmitters is radio communication of information over a distance. The information is provided to the transmitter in the form of an electronic signal, such as an audio (sound) signal from a microphone. The transmitter combines the information signal to be carried with the radio frequency signal which generates the radio waves, which is often called the carrier. This process is called modulation. The information can be added to the carrier in several different ways, in different types of transmitter.

In a frequency modulation (FM) transmitter, it is added by varying the radio signal’s frequency slightly. Many other types of modulation are used.

The antenna may be enclosed inside the case or attached to the outside of the transmitter, as in portable devices such as cell phones, walkie-talkies, and garage door openers. In more powerful transmitters, the antenna may be located on top of a building or on a separate tower, and connected to the transmitter by a feed line, that is a transmission line.

1.2                                                  PROBLEM STATEMENT

Frequency modulation transmitter is one of the basic equipment required in telecommunication laboratories. The department of Electrical Electronic Fidel Polytechnic Gboko has over the years has been suffering from shortage of frequency modulated transmitter for practical uses. These has really hindered the students from acquiring the basic knowledge of frequency modulation (FM) because all students cannot operate the available equipment at the same time owing to the fact that students are too many to work on a single transmitter, they get discouraged and refuse to concentrate on these practical.

In a bid to find solution to this problem, the idea of increasing the number of such transmitter was initiated with the hope of finding a testing solution to this problem.

1.3                                              PURPOSE OF THE PROJECT

The main purpose of this work is to allow music or other audio content from a portable media player, CD player or other portable audio system to be played through a nearby FM radio. It can either be a capability built into a portable media player, or a portable appliance that plugs into the headphone jack or proprietary output port of a portable media player or video device. The sound is then broadcast through the transmitter on an FM broadcast band frequency and picked up by the receiver. The purpose is generally to allow portable audio devices to make use of the better sound quality of a home audio system or car stereo without requiring a wired connection between them.

• OBJECTIVE OF THE PROJECT

The objective of this work is to design and construct an FM transmitter which transmits a frequency modulated signal to an fm radio. That is, to construct a device that can broadcast signals on 92.5 MHz fm broadcast band which be picked up by the receiver.

1.5                           LIMITATIONS OF THE PROJECT

The relatively low power output of FM transmitters sometimes makes it unsuitable for use in some large urban areas because of the number of other radio signals. This is compounded by the fact that strong FM signals can bleed over into neighboring frequencies making the frequencies unusable with the transmitter. Removing a car’s radio antenna has been found to significantly improve transmitter reception. The frequency of this device is limited to 92.5Mhz.

Some models which connect via ports other than the headphone jack have no means of controlling the volume, which can force the sound to transmit out from the device harshly (causing over modulation, audio distortion and possible radio interference), or too low. In theory a device could use an automatic level control or audio limiter circuit to overcome this problem although there are few (if any) devices with such a facility available out on the market yet.

1.6                                               SCOPE OF THE PROJECT

1. FM transmitter is basically a VHF colipits oscillator capable of transmitting sound or music to any standard FM receiver. The circuit works on a D.C source which makes it for a pure rectification. FM transmitter also has a capacitor microphone which picks up very weak sound signals, and discrete components such as: Transistor, Diode, Resistor, Capacitor and Inductor.
2. This project transmits frequency on 92.5MHz± 5%. The transmitting distance is l00metres. It is powered with 5volt – 15volts D.C battery using suitable F.M receiver tuned to the transmitting frequency of this project. F.M Transmitter can be used as cordless microphones, mobile phone and for public address purposes.

1.7                                          APPLICATION OF THE PROJECT

FM transmitters used in many different environments. Some of the more popular uses are churches, sporting events, fitness centers, homes, cars, correctional facilities and holiday light shows.

1.8                                           SIGNIFICANCE OF THE STUDY

The project signifies a lot in the electronic communication system which telecommunication is the vital aspect which is usually demonstrated through radio communication system the frequency modulation transmitter is applied in a lot of instance frequency modulation is used in FM radio stations scattered all over the country whose advantage is paramount compared to its counterpart AM modulation frequency modulation transmitted is equally used in a miniaturized from as wireless morpheme.

1.9                                                  DEFINITION OF TERMS

FM    –                  Frequency Modulation

VHF  –                  Very High Frequency (30MHz to 300MHz)

UHF  –                  Ultra High Frequency (300MHz to 3GHz)

VFO  –                  Variable Frequency Oscillator

VCO –                  Voltage Controlled Oscillator

PLL  –                  Phase Locked Loop

Oscillator –                    device that generates a frequency

1.10                                       METHODOLOGY

To achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Draw a block diagram.

• Test for continuity of components and devices,

1. Design and calculation for the device was carried out.
2. Studying of various component used in circuit.
3. Construction of the circuit was carried out.

• Finally, the whole device was cased and final test was carried out.

1.11                                      PROJECT WORK ORGANISATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this work is on the introduction to an fm transmitter. In this chapter, the background, significance, objective limitation and problem of an fm transmitter were discussed.

Chapter two is on literature review of an fm transmitter. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.