DESIGN AND CONSTRUCTION OF 100m FM WRELESSS TRANSMITER

PREPARED BY
PAUL-DAN OMOYELE JOHN
20EG02032

A PROJECT REPORT SUBMITTED TO THE DEPARTMENT OF

ELECTRICAL/ELECTRONICS ENGINEERING IN PARTIAL FULFILMENT OF THE
REQUIREMENT FOR THE AWARD OF THE BACHELOR OF ENGINEERING
IN ELECTRICAL/ELECTRONICS ENGINEERING OF
AJAYI CROWTHER UNIVERSITY.
Certification

I certify that this work “DESIGN AND CONSTRUCTION OF 100m FM BUGGER

CIRCUIT FOR VOICE CAPTURING” was carried out by PAUL-DAN OMOYELE JOHN
20EG02032 of the Department of Electrical/Electronics Engineering of AJAYI
CROWTHER UNIVERSITY.

Dr. Adebayo Date

(Project Supervisor).

Dr. Ajeigbe Date

(Head of Department
Dedication
I dedicate this project work to God Almighty.
ACKNOWLEDGEMENT
Glory to God almighty for the grace receives from Him in making this program a reality
despite being through the thick and thin. Gratitude goes to my parents.
Sincere appreciation goes to my project supervisor, Dr. Adebayo for his academic and
constructive critics Also, A very big thanks to my able Head of Electrical/Electronics
Engineering Department Dr. Ajeigbe for his ableness and counseling.

Moreover, my sincere gratitude goes to all teaching and non-teaching staff of

Electrical/Electronics Engineering Department for their support during the course of
study.
ABSTRACT
FM bugger is a device which generates frequency modulated signal.It is one
element of a radio system which, with the aid of an antenna, propagates an
electromagnetic signal. Standard FM broadcasts are based in the 88-108 MHz
range. The signal (from the microphone) is fed into the audio frequency (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.Fm receivers can be operated in the very high
frequency bands at which AM interference is frequently severe, commercial FM
radio stations are assigned frequencies between 88 and 108 MHz and is the
intended frequency range of transmission. The FM bugger is a device which
gives the information of one person to another in the remote location.
Normally bugger is used for finding out the status of the person like where he is
going, what he is talking etc. This FM bugger circuit is kept in a place where
there is need of listening to a conversation.

The project enhances one's practical skill and it involves both the electronics
and telecommunication engineering fields. Theoretical knowledge suchas
circuit theory,electronic circuit and principles of telecommunication learned
through several courses offered by the electrical and telecommunication
program is applied in the project.
 LIST OF FIGURES
Figure:3.1 Block by block diagram of the project 17

Figure:3.2 Circuit diagram of the project 20

Figure:4.1 Pin diagram of dynamic microphone 23

Figure:4.2 Pre amplifier circuit diagram 25
Figure:4.3 Modulation stage circuit diagram 26
Figure 6.1 pictorial diagram of the project 39
LIST OF TABLE
5.4 Bill of engineering measurements and evaluation (BEME) Table 32
TABLE OF CONTENTS
Front Page

Certification ii

Dedicationiii

Acknowledgment iv

Abstract V

List of figures vi

List of Table vii

Table of Content vii

CHAPTER ONE1

Introduction 1

Background of the study 1

Statement of the problem2

Research objectives and aim 3

Contribution to knowledge 3

Limitation of project 4

Methodology 4

Definition of terms 4

CHAPTER TWO 5
Literature review 5
Brief outline of the chapter 5
Historical background of the project 5

Theories and concept related to the project8

Electromagnetic waves 8

Modulation and demodulation 10

Methods of modulation 11

Analog modulation method 11

Digital modulation method 12

Process of modulation and demodulation 13

CHAPTER THREE 16
Methodology 16
Brief outline of the chapter 16

Research design of the project 16

Block by block (unit by unit) design of the project 17

Circuit Diagram Design of the Project 20

CHAPTER FOUR 21

Principle Of Operation Of The Project 21

Breif Outline Of The Chapter 21

Principle Of Operation Of The Fm Bugger 21

Operational Mode Of Microphone 21

Working Principle Of Microphone 22

Explanation of the various units (blocks) in the intruder system with alarm. 24

CHAPTER FIVE 24

Construction of the designed project 27

Brief outline of the chapter27

Choice Of Materials27

Construction Of The Project 28

Fabrication of Printed circuit board 28

Drilling of Holes 30

Reference designation 31

Component layout 31

Soldering procedure 32

Casing 32

Bill Of Engineering Measurements And Evaluation (Beme) Table 32

 Tests34

Continuity test 34

Operational and Range Testing 35

CHAPTER SIX 36
Conclusion,summary and recommendations 36
Summary of the project chapter by chapter 36

Problems encountered 37

Recommendations 38

References 39
CHAPTER ONE

1.0 Introduction

This chapter provides an overview of the project by giving description of the

problem. Chapter one discusses about the background of the project, problem
description,aims and objective and project limitations.

In electronics and telecommunications, a bugger or transmitter is an

electronic device which produces radio waves with an antenna. The bugger itself
generates a radio frequency alternating current, which is applied to the antenna.
When excited by this alternating current, the antenna radiates radio waves.
Buggers are necessary component parts of all electronic devices that
communicate by radio, such as radio and television broadcasting stations, cell
phones, walkie-talkies,wireless computer networks, Bluetooth enabled devices,
garage door openers, two-way radios in aircraft,ships,spacecraft, radar sets and
navigational beacons.

The term bugger/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.

1.1 Background Of Study The

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 crisis 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
receiver. An FM bug is a 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. In this project frequency modulation
(FM) is used because it transmits 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 108MHz.

According to the Institute of Electrical and Electronics Engineering

(IEEE)laws,the FM bug is a “free-use” device without license. The law is important
since the usage of the device could invade privacy by retrieving other people's
voices.There was then the need to protect the rights of users who were not
authorities (European Academic Research, 2013). This bugger is a device which
gives the information of one person to another in the remote location. Normally
bugger is used for finding out the status of the person like where he is going, what
he is talking etc.This FM bugger circuit is kept in a place where there is need of
listening to a conversation
 1.2 Statement Of Problem

Due to the high risk to lives, FM bugger circuit will be used to replace human
spy for their protection. This circuit can be used at any place to transmit audio
signals using FM transmission, especially at institutions and organizations.

Every day of our work and in our free time, we come in contact with and use
a variety of modern communication system and communication media, the most
common being the telephone, radlio,television and internet. Through these
media,we are able to communicate with people in different continent and transact
our daily business and received information about various development and events
of note and that occurs all around the world.
The continuous need of human to pass information and their insatiable
nature to share information gave rise to the inception of any radio communication
system.In other words, a bugger transmits intelligence from one point or place to
another.Communication may be unidirectional as in the case of sound and television
broadcasting or it may be bidirectional with most radio television system. At the
transmitting of the system, the signal must modulate a suitable carrierfrequency
spectrum and then be amplified to the necessary transmitter power level to give it
enough strength to travel over a reasonable distance.

1.3 Research Aim And Objectives

The aim of this project is to construct an FM bugger circuit capable of

picking up information (sound waves) and transmitting over a range of 100m.

The objectives of this project include;

·To review bugger circuit and their ranges.

·To determine the best frequency for transmission.
 · To understand how antenna are made to receive signals of a particular
frequency only.

· To test the circuit and its range.

1.4 Contribution To Knowledge

The completion of this project would allow the transmission of information

over a reasonable coverage of area like a mini office or schools without any cost of
subscription or service.

This project could also be used for spying and getting information for
security reasons or intelligent investigation by detectives and agencies.
The medium of FM bugger circuit has other positive advantages, like: Free
from subscription charges, simplicity, possible to listen to at a particular within the
specified range and possible to listen to while doing something else.

This project has also added to my understanding on simple radio

communication system,wireless transmission of signals and bugging of
information.

1.5 Limitation Of Project

The scope of this project is to construct an FM bugger that can transmit

sound waves over a range of 100m effectively.

The limitation of this project is that the sound waves become partially lost
or totally,when the proposed range (100m) has been exceeded. That is the
transmission capabilities of the antenna of the bugger circuit. The Transmitter and
receiver Frequency is 107.9fm.

1.6 Methodology
 This project will be created by consulting journals, textbooks, term
papers,and other resources related to the topic. Information and knowledge of
experts also made a large deposit of this work achievable, especially while
designing this project.

The internet also formed a large part of the methodology used to make
the project as related project works were researched.

1.7 Definitions Of Terms

Microphone: A device (transducer) used to convert sound waves into a varying

electric current; normally fed into an amplifier and either recorded or broadcast.
Antenna: An apparatus to receive or transmit electromagnetic waves and convert
respectivelyto or from an electrical signal.

Multiplexing: is a method by which multiple analog or digitl signals are combined

into one signal over a shared medium. The aim is to share a scarce resource.

Audio Bug:is a circuit capable oftransmitting sound waves over a range of

distance.It is synonymous with transmitter.
CHAPTER TWO

2.0 Literature Review

2.1 Brief Outline Of The Chapter

This chapter contains the historical background, bodies of previous

works,experiments and books relating to the project. The chapter further explains
the theories and concepts relevant to the project.

2.2 Historical Background Of The Project

 The first primitive radio transmitters, which evolved into an FM bugger,
(called spark gap transmitters) were built by German physicist Heinrich Hertz in
1887 during his pioneering investigations of radio waves. These generated radio
waves by a high voltage spark beween two conductors.

Beginning in 1895,Guglielmo Marconi developed the first practical radio

communication systems using these transmitters, and radio began to be used
commercially around 1900. Spark transmitters could not transmit audio (sound)
and instead transmitted information by radiotelegraphy, the operator tapped on a
telegraph key which turned the transmitter on and off to produce pulses of radio
waves spelling out text messages in Morse code.

These spark-gap transmitters were used during the first threedecades of

radio (1887-1917),called the wireless telegraphy or "spark" era. Because they
generated damped waves, spark transmitters were electrically "noisy". Their
energy was spread over a broad band of frequencies, creating radio noise which
interfered with other transmitters. Damped wave emissions were banned by
international law in 1934.
Two short-lived competing transmitter technologies came into use after
the turn of the century, which were the first continuous wave transmitters: the
arc converter (Poulsen arc) in 1904 and the Alexanderson alternator around
1910,which were used into the 1920s.

All these early technologies were replaced by vacuum tube transmitters

in the 1920s, which used the feedback oscillator invented by Edwin Armstrong
and Alexander Meissner around 1912, based on the Audion (triode) vacuum
tube invented by Lee De Forest in 1906. Vacuum tube transmitters were
inexpensive and produced continuous waves,and could be easily modulated to
transmit audio (sound)using amplitude modulation (AM). This made AM radio
broadcasting possible,which began in about 1920.

Practical frequency modulation (FM) transmission was invented by Edwin

Armstrong in 1933,who showed that it was less vulnerable to noise and static
than AM. The frst FM radio station was licensed in 1937. Experimental television
transmission had been conducted by radio stations since the late 1920s,but
practical television broadcasting didn't begin until the late 1930s. The
development of radar during World War II motivated the evolution of high
frequency transmitters in the UHF and microwave ranges, using new active
devices such as the magnetron,klystron, and travelling wave tube.

The invention of the transistor allowed the development in the 1960s of

small portable buggers and transmitters such as wireless microphones, garage
door openers and walkie-talkies. The development of the integrated circuit (IC)
in the 1970s made possible the current proliferation of wireless devices, such as
cell phones and Wi-Fi networks, in which integrated digital transmitters and
receivers (wireless modems) in portable devices operate automatically, in the
background, to exchange data with wireless networks.
The need to conserve bandwidth in the increasingly congested radio
spectrum is driving the development of new types of transmitters such as
spread spectrum,trunked radio systems and cognitive radio. A related trend
has been an ongoing transition from analog to digital radio transmission
methods.Digital modulation can have greater spectral efficiency than analog
modulation; that is it can often transmit more information (data rate) in a given
bandwidth than analog, using data compression algorithms. Other advantages
of digital transmission are increased noise immunity, and greater flexibility and
processing power of digital signal processing integrated circuits.
2.3 Theories And Concepts Related To The Project

The major theories and concepts related to this project are propagation
of electromagnetic waves, modulation and demodulation of signals and
transmission.These concepts are the foundational principles on which the FM
buggers are built.

2.3.1 Electromagnetic Waves

Electromagnetic waves are radiated by electric charges when they are

accelerated. Radio waves,electromagnetic waves of radio frequency, are
generated by time-varying electric currents, consisting of electrons flowing
through a metal conductor called an antenna which is changing their velocity
and thus accelerating.

An alternating current flowing back and forth in an antenna will create

an oscillating magnetic field around the conductor. The alternating voltage will
also charge the ends of the conductor alternately positive and negative,
creating an oscillating electric field around the conductor. If the frequency of
the oscillations is high enough, in the radio frequency range above about 20
kHz, the oscillating
coupled electric and magnetic fields will radiate away from the antenna into space
as an electromagnetic wave, a radio wave.

An FM bugger or radio transmitter is an electronic circuit which transforms

electric power from a power source into a radio frequency alternating current to
apply to the antenna, and the antenna radiates the energy from this current as
radio waves. The transmitter also impresses information such as an audio or video
signal onto the radio frequency current to be carried by the radio waves. When
they strike the antenna of a radio receiver, the waves excite similar (but less
powerful) radio frequency currents in it. The radio receiver extracts the
information from the received waves.
A practical radio transmitter mainly consists of the following parts:

·In high power transmitters, a power supply circuit to transform the input
electrical powerto the higher voltages needed to produce the required
power output.
·An electronic oscillator circuit to generate the radio frequency signal. This
usually generates a sine wave of constant amplitude called the carrier
wave,because it serves to "carry" the information through space. In most
modern transmitters, this is a crystal oscillator in which the frequency is
precisely controlled by the vibrations of a quartz crystal. The frequency of
the carrier wave is considered the frequency of the transmitter.

·A modulator circuit to add the information to be transmitted to the carrier

wave produced by the oscillator. This is done by varying some aspect of the
carrier wave. The information is provided to the transmtter as an electronic
signal called the modulation signal.
2.3.2 Modulation And Demodulation

Modulation is the process of varying one or more properties of a

periodic waveform,called the carrier signal, with a modulating signal that
typically contains the information to be transmitted, WVhile Demodulation is
the process of extracting the original information-bearing signal from a carrier
wave.

A modulator is a device that performs modulation. A demodulator is a

device that performs demodulation, the inverse of modulation. A modem (from
modulator-demodulator) can perform both operations.

The aim of analog modulation is to transfer an analog baseband (or low

pass)signal,for example an audio signal or TV signal, over an analog band pass
channel at a different frequency, for example over a limited radio frequency
band or a cable TV network channel. The aim of digital modulation is to transfer
a digital bit stream over an analog communication channel, for example over
the public switched telephone network (where a band pass filter limits the
frequency range to 300-3400Hz) or over a limited radio frequency band. Analog
and digital modulation facilitate frequency division multiplexing (FDM), where
several low pass information signals are transferred simultaneously over the
same shared physical medium, using separate pass band channels (several
different carrier frequencies).

The aim of digital baseband modulation methods, also known as line

coding,is to transfer a digital bit stream over a baseband channel, typically a
non-filtered copper wire such as a serial bus or a wired local area network.

The aim of pulse modulation methods is to transfer a narrowband

analog signal, for example, a phone call over a wideband baseband channel or,
in some of the schemes, as a bit stream over another digital transmission
system.
In music synthesizers, modulation may be used to synthesize waveforms
with an extensive overtone spectrum using a small number of oscillators. In this
case, the carrier frequency is typically in the same order or much lower than the
modulating waveform (see frequency modulation synthesis or ring modulation
synthesis).

2.3.3 Methods Of Modulaton

2.3.3.1 Analog Modulation Methods

In analogue modulation, the modulation is applied continuously in

response to the analogue information signal. Common analogue modulation
techniques include:

Amplitude modulation (AM): here the amplitude of the carrier signalis varied in
accordance with the instantaneous amplitude of the modulating signal. Examples
include:
 1. Double-sideband modulation (DSB)
2. Double-sideband modulation with carrier (DSB-WC) (used on the AM radio
broadcasting band)

3. DDouble-sideband suppressed-carrier transmission (DSB-SC)

4. Double-sideband reduced carrier transmission (DSB-RC)
5. Single-sideband modulation (SSB, or SSB-AM),etc.

Frequency modulation (FM): here the frequency of the carrier signal is varied in
accordance with the instantaneous amplitude of the modulating signal.

Phase modulation (PM): here the phase shift of the carrier signal is varied in
accordance with the instantaneous amplitude of the modulating signal.
Transpositional Modulation (TM): in which the waveform inflection is modified
resulting in a signal where each quarter cycle is transposed in the modulation
process. TM is a pseudo-analog modulation (AM).

2.3.3.2 Digital Modulation Methods

In digital modulation, an analog carrier signal is modulated by a discrete

signal. Digital modulation methods can be considered as digital-to-analog
conversion and the corresponding demodulation or detection as analog-to-digital
conversion. The changes in the carrier signal are chosen from a finite number of M
alternative symbols (the modulation alphabet).

Fundamental digital modulation methods

The most fundamental digital modulation techniques are based on keying:

·PSK (phase-shift keying): a finite number of phases are used.

·FSK(frequency-shift keying): a finite number of frequencies are used.
 · ASK (amplitude-shift keying): a finite number of amplitudes are used.
·QAM(quadrature amplitude modulation): a finite number of at least two
phases and at least two amplitudes are used.

In all of the above methods, each of these phases, frequencies or

amplitudes are assigned a unique pattern of binary bits. Usually, each phase,
frequency or amplitude encodes an equal number of bits. This number of bits
comprises the symbol that is represented by the particular phase, frequency or
amplitude.

For example, with an alphabet consisting of 16 alternative symbols, each

symbol represents 4 bits. Thus, the data rate is four times the baud rate.
In the case of PSK, ASK or QAM, where the carrier frequency of the
modulated signal is constant, the modulation alphabet is often conveniently
represented on a constellation diagram,showing the amplitude of the I signal at
the x-axis, and the amplitude of the Q signal at the y-axis, for each symbol.

2.3.3.3 Processes Of Modulation And Demodulation

These are the general steps used by the modulator to transmit data:

·Group the incoming data bits into code words, one for each symbol that will
be transmitted.
Map the code words to attributes, for example, amplitudes of the I and Q
signals (the equivalent low pass signal), or frequency or phase values.
·Adapt pulse shaping or some other filtering to limit the bandwidth and form
the spectrum of the equivalent low pass signal, typically using digital signal
processing.
·Perform digital to analog conversion (DAC) of the I and Q signals (since today
all of the above is normally achieved using digital signal processing, DSP).
·Generate a high-frequency sine carrier waveform, and perhaps also a cosine
quadrature component.
 ·Amplification and analog band pass filtering to avoid harmonic distortion and
periodic spectrum.

At the receiver side, the demodulator typically performs:

·Band pass filtering.

Automatic gain control, AGC (to compensate for attenuation, for example
fading).
·Frequency shifting of the RF signal to the equivalent baseband I and Q
signals,or to an intermediate frequency (IF) signal, by multiplying the RF
signal with a local oscillator sine wave and cosine wave frequency (see the
super heterodyne receiver principle).
Sampling and analog-to-digital conversion (ADC) (sometimes before or
instead of the above point, for example by means of under sampling).
·Equalization filtering, for example, a matched filter, compensation for
multipath propagation, time spreading, phase distortion and frequency
selective fading, to avoid inter symbol interference and symbol distortion.
·Detection of the amplitudes of the I and Q signals, or the frequency or phase
of the IF signal.
Quantization of the amplitudes, frequencies or phases to the nearest
allowed symbol values.
Mapping of the quantized amplitudes, frequencies or phases to
codewords (bit groups).

Parallel-to-serial conversion of the codewords into a bit stream.

Pass the resultant bit stream on for further processing such as removal of
any error-correcting codes.
 This is common to all digital communication systems, the design of both
the schemes are possible because the transmitter-receiver pair has prior
knowledge of how data is encoded and represented in the communications
system. In all digital communication systems, both the modulator at the
transmitter and the demodulator at the receiver are structured so that they
perform inverse operations.

Asynchronous methods do not require a receiver reference clock signal

that is phase synchronized with the sender carrier signal. In this case,modulation
symbols
(rather than bits, characters, or data packets) are asynchronously
transferred.The opposite is synchronous modulation.
CHAPTER THREE

3.0 Methodology

3.1 Brief Outline Of The Chapter

In this chapter, the methodology, the research design and the block by
block (unit by unit) design of the project are discussed in details.

The proje

3.2 Research Design Of The Project

ct is a 100m FM bugger system designed to helplisten to a conversation of

a third party from a known location under limited distance of 100m.

The technology used in picking up the conversation or voice from the

location,as well as every other units all to the antenna, was determined to suit
our purpose of an efficient FM bugger of a 100m range. The major
components in this project includes; microphone,transistor,resistor capacitor
and antenna.
 To achieve transmission, the signal to be transmitted is first converted to
electrical signal or to the signal form of the transducer. Then the signal is
joined with a stronger signal known as the carrier signal through a process
known as modulation,to enable the signal travel large distance with minimal
loss.

The modulated signal is then transmitted for a particular frequency on

which the receiver must be tuned into, to get the signal. The signal is then
demodulated and the information-bearing signal is what is left.
3.3 Block By Block (Unit By Unit) Design Of The Project

The design of 100m FM bugger is clearly illustrated by the block diagram

showvn below:

Transmitter Section:

Receiver Section:

Fig:3.1 Block by block diagram of the project.

 Power Supply Stage

The source of power supply used in the design is a 9V DC battery. This

is completely free from AC ripples that cause electrical noise especially in
oscillation circuits. The circuit for this project consists of track-etched inductor
whose reactance is determined by voltage level. Any change in this voltage
level as a result of ripples or fluctuations existing in the power supply is
converted to equipment change in the inductive reactance.
This change in inductive reactance is converted by the circuit to variation
or drift in oscillation frequency of the transmitter. Initially, when the bugger was
connected to ordinary 12V power supply consisting of transformer rectifier and
filter circuit,its output was seriosly affected by frequency drift and electrical noise.

Input Stage

The input section contains the microphone which convert sound waves
into an electrical waves, when a voice is heard or a musical instrument is played,
the varying air pressure on the microphone generate audio electrical signal which
has a frequency as that of the original voice sent initially from the microphone
input.This frequency is very low and it needs to be stepped up before its
transmission and thus we feed it into the pre amplifier so as to raise or
strengthen the weak signal.

Pre-Amplifier Stage

The pre-amplifier boosts the audio signal (voice) levels from several milli-
volts to higher voltage for the modulator. Usually a high pass filter network is
added between pre-amplifier and modulator stage. This high pass filter acts as
pre-emphasis network to improve the signal to noise level of FM transmission at
higher frequency. The pre-emphasis network is optional. However,the receiver
 will suffer from distortion at higher frequency of audio signal if this stage is
ignored.

Modulation/Oscillation Stage

In this stage, the oscillator helps to generate high frequency which is known
as carrier wave. With the carrier signal generated from oscillator, the modulator
modulates the carrier wave with input signal from pre-amplifier stage that's they
are superimposed on each other to generate modulating waves or radio waves.
This output operating frequency of the generated FM output is still not
high enough to be transmitted through free space. Thus, several stages of
frequency multiplier are put to increase the operating frequency. After going
through a number of multipliers, the attenuation of signal level is compensated
by the final stage power amplifier.

Power Amplifier Stage

This stage could be divided into two sub stages for clarity; the voltage
amplification stage and driver stage. The voltage amplification sub stage makes
the modulated signal stronger to undergo the further stages. This purpose is
achieved by using Class A amplifiers and gain of the essential voltage is attained
by using two or more RC coupled Class A amplifier.

While, the driver sub stage can be treated as a middle stage, which lies
between the voltage amplification sub stage and the final stage. The voltage
amplifying stage alone is not sufficient to drive the output stage. Because, it
has a low input impedance. Therefore,this stage acts as a middle stage that
can produce the gain of the current and gain of the sufficient power.

Output Stage

The output stage is connected to the antenna wvhich is used to

transmit the signal. This stage increases the power gain and makes output
with less power loss.The transistor arrangement used is the push-pull
 arrangement because of its advantages which includes high efficiency, high
power output, DC current cancellation, cancellation of even-harmonics, and so
on.
3.4 CIRCUIT DIAGRAM DESIGN OF THE PROJECT

Fig:3.2 Circuit diagram of the project.

100m FM Bugger Circuit For Voice Capturing.

CHAPTER FOUR

4.0 Principle Of Operation Of The Project

4.1 Breif Outline Of The Chapter

This chapter contains the principle of operation of the FM bugger,explanation of

its various units and interrelationship among them and the detailed circuit
diagrams.

4.2 Principle Of Operation Of The Fm Bugger

The circuit is built with a power supply, resistor, inductor, antenna and
capacitor.The power supply unit is made up of a 9volts battery and augment the
current for longer usage of the project then a low pass filter capacitor is employed
to filter unwanted ripples that will be generated in the battery. Microphone act as
the main component that help in converting sound waves into an electrical wave
when a sound is heard. The other components help in amplifying low waves
generated from the microphone before it's been radiated into the receiver.

4.2.1 Operational Mode Of Microphone

A microphone, is a transducer that converts sound into an electrical

signal.Microphones make it possible to send the sounds of our voices, our
music, and the noises in our world to other places and other times. How do
microphones work?Let's take a closer look.

How does a microphone turn sound energy into electrical energy? Like this:

Simple artwork showing how microphones work.

1. When a sound is made, sound waves created by the voice carry energy toward
the microphone. This sound wecan hear is energy carried by vibrations in the
air.

2. Inside the microphone, the diaphragm (much smaller than you'd find in a
loudspeaker and usually made of very thin plastic) moves back and forth
when the sound waves hit it.

3. The coil, attached to the diaphragm, moves back and forth as well.
4. The permanent magnet produces a magnetic field that cuts through the coil.As
the coil moves back and forth through the magnetic field, an electric current
flows through it
5. The electric current flows out from the microphone to an amplifier or sound
recording device. By using this current to drive sound recording
 equipment,you can effectively store the sound forever more. Or you could
amplify (boost the size of) the current and then feed it into a loudspeaker,
turning the electricity back into much louder sound.

4.2.2 Working Principle Of Microphone

There are many types of microphones such as the dynamic,ribbon,condenser and

crystal microphone that can be used for this project but the most easy to work
with and available one in the market is dynamic microphone.

sound pressure
variations Dynamic
Fig:4.1 Pin diagram of dynamic microphone

Sound moves the cone and the attached coil of wire moves in the field of a
magnet.The generator effect produces a voltage which “images" the sound
pressure variation characterized as a pressure microphone.

The geometry of a dynamic microphone is like that of a tiny loudspeaker, and that
is not just a coincidence. A dynamic microphone is essentially the inverse of a
dynamic loudspeaker. In a dynamic microphone, the sound pressure variations
move the cone,which moves the attached coil of wire in a magnetic field, which
generates a voltage. In the loudspeaker, the inverse happens: the electric current
associated with the electrical image of the sound is driven through the coil in the
magnetic field,generating a force on that coil. The coil moves in response to the
audio signal,moving the cone and producing sound in the air.
4.3 Explanation Of The Various Units (Blocks) In The Intruder System With
Alarm.

POWER SUPPLY

Absolutely all electronics equipment make use of DC voltage from either a

battery or converted from an energy source such as AC power line, the solar
energy panels,the thermal energy converted (thermocouple) and others.
Here we make use of 2lithium batteries connected in parallel which gives.
3.7Vdc and increase the current for longer duration before
recharging.Dynamic microphone desires a ripple free DC supply and thus we
filtrate the output supply by a capacitor.

PRE-AMPLIFIER

The pre-amplifier boosts the audio signal (voice) levels from several milli-
volts to higher voltage for the modulator. Usually a high pass filter network
is added between pre-amplifier and modulator stage. This high pass filter
acts as pre-emphasis network to improve the signal to noise level of FM
transmission at higher frequency. The pre-emphasis network is optional.
However, the receiver will suffer from distortion at higher frequency of
audio signal if this stage is ignored.

The highinput impedance produces a reasonable voltage level from the

charge output of the microphone capsule. The noise floor of the pre-
amplifier is dependent on the capacitance load imposed by the
microphone capsule. In general,larger capsules with the highest
 capacitance yield the lowest noise. The diagram below shows the circuit
diagram of pre amplifier.

PRE-AIPUIFIER

Fig:4.2 Pre Amplifier Circuit Diagram

·MODULATION

In this section we make use of a low power high frequency bipolar transistor
2N222 as our oscillator couple with capacitor and resistor. With the carrier signal
generated from oscillator, the modulator modulates the carrier wave with input
signal from pre-amplifier stage.The diagram below shows the circuit diagram of
pre amplifier.
 Fig:4.3 Modulation stage circuit diagram

OUTPUT STAGE

Output Stage

The output stage is connected to the antenna which is used to transmit the signal.This stage
increases the power gain and makes output with less power loss. The transistor arrangement
used is the push-pull arrangement because of its advantages which includes high efficiency,high
power output, DC current cancellation, cancellation of even-harmonics,and so on.
CHAPTER FIVE

5.0 CONSTRUCTION OF THE DESIGNED PROJECT

5.1 BRIEF OUTLINE OF THE CHAPTER

This chapter contains a detailed description of how the project is made

from the power supply unit to the last unit. It also explains the reasons for
choosing the various components used in the construction.

It also contains the BEME table for the construction of the project, as well
as the results of the project when it was tested.

5.2 Choice Of Materials

1. The capacitors used are all electrolytic capacitors because the circuitry of the
project is polarity sensitive.

2.9 V battery was selected for the power supply due to their light weight and
power capacity.
3. Electret microphone is best for any project which involves microphone and
low frequency sound waves; this is why it was chosen in this project.

4.The different resistors in the circuitry of this project are 0.5 watts since the
project is nota heavy power device.
5. The analog radio. was chosen over the popular digital ones because it
allows manual tuning and thereby gives a wide range of frequency to choose
from.

6. The plastic enclosure was used to corroborate the intention to hide the
original purpose of the device.

7.Printed circuit board was chosen over the usual and conventional use of
veroboard to make the device more compact.

5.3 Construction Of The Project

5.3.1 Fabrication of Printed circuit board

The fabrication process of the printed circuit boardstarts from

screening.The following materials were used at the screening stage;emulsion
transparent glass,hard book, foam water mesh (silk) and sun light. The
following sequences were carefully followed to ensure quality transfer of the
master printed circuit pattern to the copper side surface.
 Procedures:

Mixture: Steizer and emulsion were mixed and poured on the mesh (silk). A
smooth piece of plastic was used to rub the mixture repeatedly on the silk
until the mixture had vanished on this side. The mixture then reappeared
on the opposite side,and turning to that side, and using the plastic material
the mixture ran gently along this
side until it vanishes and reappeared at the initial side. The process of turning
and rubbing stopped when the mixture was completely absorbed and could
not significantly appear on either side.

When the mixture disappeared from either side, the silk was allowed
to dry thoroughly for about 30 minutes. The terms coating and curling are
used to describe the vanishing and reappearing of the mixture at both sides
of the mesh. It was done under a shade so that light rays did it fall on it.

Screening: The film (the bold black master print pattern) was being placed on
the silk. The transparent glass, rectangular in shape, was placed under the
silk directly opposite the film. The entire arrangement constitutes the
assembly. The assembly was brought to reach the degree of polymerization
was dependent on the light intensity.

Dispatch: After the thirty seconds count to the sun was certified, the
assembly was carefully returned to the shade and dispatched (de coupled).
Developing: After de-coupling the assembly, foam was dipped into clean water
and squeezed into the mesh repeatedly for three minutes. The foam was gently
rubbed on the silk so that a bright white line of the pattern showed up.

Having ascertain the appearance of the film (on the silk) water was
poured continuously on both sides of thesilk. After a while the foam was rubbed
on the
wetted side, and the appearance of the pattern increased. This recycling
event continued until the entire printed circuit diagrammatic pattern was
fully cured the silk was allowed todry completely.

When the mesh had completely dried, a proportionate amount of

ink called sticker ink was poured on the coated side of the mesh. The resist
coated copper surface was placed opposite directly under the coated silk on
a flat surface.The ink was run evenly along the silk with plastic materials,
then the diagrammatic pattern appeared unto the resist copper side and the
silk was removed to dry the board completely. Initially the copper side
surface was coated with a gray colored resist material. An electrician's knife
was used to remove to the resist material from areas not covered with the
conductor routing imaged pattern.

Finally, the board was thoroughly washed with detergent and rinsed
with much water then allowed to dry completely. It was then ready for
etching.The etching left only the required lines of circuit diagram and
removed every copper on the surface of the board.

5.3.2 Drilling of Holes

Holes were drilled to produce openings through the printed circuit

board in order to form electric connections between conducting pathways.
The holes were drilled in such ways than only one conductor's lead or wire
passes through.
5.3.3 Reference designation

Components generally were inserted opposite copper sideso that

their terminals would not bridge or short circuit. To show the position each
component enters;reference designation was drawn opposite copper surface
to correspond with the circuitry opposite.

5.3.4 Component layout

The design of electronic circuit wiring takes into account, most

importantly,component placement, wiring density and the functional
performance of the entire system the parts and component of this design
were carefully spaced to provide even diagram balance between blank
spaces and lines. Enough spaces were left in the area near symbol to avoid
crowding of reference information.
 Resistor diodes, transistors and capacitor were inserted into their
reference designation using terminal and polarity identification techniques.
All components were mounted approximately 5mm above the panel and
excess leads of wires were cut to about 2mm above the copper side surface.
The cutting or trimming of the excess leads was done after soldering has
been completed.
5.3.5 Soldering procedure

Every component inserted on the printed circuit board PCB was

carefully and neatly soldered to avoid being pulled out. The soldering iron was
allowed to heat properly to ensure quick melting of the alloy (60/40) lead. A
40 watt soldering iron was used to avid overheating the components. Soft
soldering was used because it is more suitable for light points in steel,
copper,brass and electronics works.

5.3.6 Casing

Several materials can be used for constructing the case of this project both for
commercial and instructional purposes, but the plastic case was adopted for
this project. It is readily available.

5.4 Bill Of Engineering Measurements And Evaluation (BEME) Table

S/N Component Quantity Unit Price(N) Total Price(N)

 1 47kΩ Resistors 10 30 300

2 330Ω Resistors 10 20 200

3 10kΩ Resistors 10 20 200

4 1μF Capacitors 10 30 300

5 4.7pF Capacitors 10 30 300

6 100μF Capacitors 10 30 300

7 10μF Capacitors 10 30 300

8 50pF Variable capacitors 10 100 1000

9 100nH Inductors 6 500 3,000

10 9V battery 1 500 500

11 Electret Microphone 2 3500 7,000

12 NPN transistors 10 70 700

13 Plastic case 1 2000 2000

14 Switch 1 200 200

15 Antenna cable 3meters 250 750

17 Printed circuit board 2 2500 5,000

18 Connecting wire 4meters 250 1000

19 Variable capacitor 2 250 500

 20 Miscellaneous 5000

Total 24,850

5.5.1 Continuity Test

When all the components had been soldered on the printed circuit board
(PCB)continuity test was carried out before the connecting the system to power
supply.The test revealed open circuit faults, which could be due to:

1.A break in the circuit.

2. The failure of a component leading to it having an unusually high resistance or

3. An increase in the insulation at certain points caused by dirt, grease or corrosion.

4. It also revealed that short circuit faults which were due to;7521

5.The failure of a component leading to it having an abnormally low resistance.

6.The touching of uninsulated parts of the component terminal

7. The effects of moisture lying between conducting paths which create links of
lower resistance than the component or.

8.Solder bridges between the terminals.

When all the components had been soldered on the printed circuit board
(PCB)continuity test was carried out before the connecting the system to the
battery.The test revealed open circuit faults due to a break in the circuit and
the failure of some
components. The components were replaced and the continuity test was carried
out again.

5.5.2 Operational and Range Testing

After the continuity test was passed and all connection seemed perfect,the
device was powered to test for its operation and the transmitter range testing. The
operational test shows the efficiency of the device. While the range testing
determines the distance from transmitter its signal will be received.

This test required an audio player and analog radio. The audio player was
placed directly at the microphone while the radio produced the sound. The test
also requires an antenna. The radio receiver set to FM band was tuned gradually to
capture the main frequency then it was moved away from the transmitter to about
100m. It sounded clear.
CHAPTER SIX

6.0 Conclusion,Summary And Recommendations

6.1 Summary Of The Project Chapter By Chapter

The first chapter of this project gives a clear introduction about the FM
bugger.It further explains the background of the project, the reasons for the
project,the aims to be achieved from the completion of the project, as well as the
contribution of the project to knowledge. It tells the scope of the project too.

The second chapter contains every work related to the project. It shows the
evolution of the FM bugger from the earliest stage to the latest technology and
describes the theories involved. It gives an overview of the project.

The third chapter is an explanation of the research design used for the
project.It explains the design of the project block by block,giving a thorough
breakdown of the whole project and its circuitry.

The fourth chapter tells how the project works as a whole; the sequential
transmission of signal to the last part. It also contains the functions of each unit in
construction and operation of the project. It is an elaborate version of the chapter
three.
The fifth chapter is the documentation of how the project was made. It gives
the detailed description of processes involved, outlined in the order of
construction.It tells reasons for choosing each component for the construction and
the cost evaluation of the project. It shows the tests carried out on the project as
well.

The last chapter is a summary of the whole project work; the conclusion. It
also documents some recommendation for further researches.

6.2Problems Encountered
1.High costof components: Prices of the materials used were expensive because
most of them were sold in bulk and ordered online. Some were imported from
other countries.

2.Unavailability of some components: Electret microphone,printed circuit boards

were imported from the US. It took several weeks before it was delivered due to
the pandemic savaging the universe

3. Getting the right circuit diagram: Getting the perfect circuit diagram was not
easy, the perfect circuit was gotten after the fifth trial and PCB was made for
each.Some did work, but the 100m range was not achieved.
6.3. Recommendations

1.Students should be implored to know how to make printed circuit board. It

makes electronics project easier, smaller and better.

2. Students should be provided with functional materials and equipment

especially in areas of test and instrumentation.
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