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CONSTRUCTION OF AN FM TRANSMITTER

ABSTRACT

This project work is on the construction of an F.M transmitter this system consists of four discrete modules namely the audio frequency (AF) amplifier (class A) the modulator the master oscillator and the radio frequency (RF) amplifier (ClassC) these formed the conventional events for building FM transmitter here the signal (from the microphone) is fed into the (AF) for amplification then to the modulator which combines the modulating signal with the carrier wave transports the modulated signal through (RF) for final amplification to the antenna via the resonance circuit for propagation the transmitter was tested using radio receiver it transmitted clearly at the frequency of 108 MH3 and the coverage was to metres.

CHAPTER ONE

INTRODUCTION

Information transmission is very vital to human life just as the early men used sticks to produce sound which indicates the location of each other as they wander about also down to the middle era when town crises come into play for the same information propagation to be transmitted from one point to another with the aid of radio communication which necessities the application of radio transmitter and receive.

A radio transmitter is device whose major function is to send information (intelligence) from one point to another in most cases the information to be transmitted are voice music and code signals. However the transmission of radio signal is done with the aid of electrical resonance this is when the frequency of the receiver is equal to the incoming one from the transmitter resonance is observed which is the totality of radio communication I personally decided to work on frequency modulation (FM) transmitter because it transmitted radio signal which is less distorted than other wave bands like amplitude modulation and short wave band. The frequency on the tuning dial ranges from 88MHZ to 108MH3.

In transmitter configuration a sound is fed at the microphone which is the transducer that converts the physical sound into the electrical signal which is usually amplified by the fist electronic circuit (audio frequency amplifier class A) whose output is fed into a modulator which fields a frequency modulated output fed into the final stage (radio frequency amplifier class C) then to the antenna which radiates the radio signal into the atmosphere. All these process were because audio frequency signal cannot be radiated out from the antenna directly because transmission at audio frequency is not particle this is because of audio frequency signals.

1. They have reactively short range

2. It everybody started transmitting these low frequency signal directly mutual interference will render all of them ineffective 

3. The size of antenna required for their would be large.

Furthermore for proper understanding of this information transmission-using transmitter I here by introduce the concept of modulation and demodulation.

CONCEPT OF MODULATION AND DEMODULATION 

Modulation is technically the process of combining an audio frequency signal (low frequency signal) with a high frequency oscillator. However the audio frequency signal which is being transmitted super imposes on the carrier wave that transports it to the out put of the radio frequency amplifier into the antenna this audio frequency signal other wise known as modulating signal is being amplifier by the radio frequency amplifier in order to overcome air impendence as it travel from the transmitter to the receiver.
Demodulation in the other hand is the process of separating or recovering the signal (modulating signal) from the modulated earlier wave it is the opposite of modulation and it is performed at the receiving end (radio receiver.

TYPES OF MODULATION 

There are three types of modulation namely amplitude modulation (AM) frequency modulation (FM) and phase modulation (PM).

1. Amplitude modulation (AM) is the types of modulation in which the information signal (audio frequency signal) varies the amplitude of the earlier wave without changing it’s frequency. As the name implies it is only the amplitude of the earlier wave without changing it’s frequency. As the name implies it is only the amplitude that is being varied while the frequency is kept constant as the wave travels.

2. Frequency modulation (FM) is the type of modulation is which the modulating signal varies the frequency of the carrier wave here it is only the frequency of the signal in frequency modulation carrier information (intelligence) is carried is variations in its frequency.

3. Phase modulation (PM) is the type of modulation that varies the phase of the radiated wave at the modulating frequency and by an angle, which is proportional to the amplitude of the modulating wave from.

OBJECTIVE OF THE PROJECT

The objective of this project is to construct an electronically operated system known as FM transmitter capable of transmitting a frequency modulated signal with a littler or no distortion into the atmosphere for dissemination secondly to aid the gradating student into a season research activities that will carry them along during the professional practice as a scientist.

SIGNIFICANCE OF THE PROJECT

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