International Journal of Applied Engineering Research ISSN 0973-4562 Volume 12, Number 18 (2017) pp.

7516-7523
© Research India Publications. http://www.ripublication.com

The Design and Construction of a Frequency Modulated (FM) Transmitter

with Output Capacity of 10 Watts and Range above 4km

Ogbuanya T.C. 1, Sule Abu1 and Bakare J 1*

1
Department of Industrial Technical Education, University of Nigeria, Nsukka. Nigeria.
(*Corresponding Author: Bakare J)
1
Orcid iD: 0000-0002-1656-0147

Abstract usually has a power supply, an oscillator, a modulator and

amplifiers for audio frequency (AF) intermediate frequency
A rapidly growing demand for the use of FM transmitter
(IF) and radio frequency (RF). Transmitters are sometimes
exists among individuals and institutions. The FM transmitters
classified according to the signal information they process and
are however complex equipment demanding high power
radiate. Television transmitters processes sounds and picture
supply high voltage system design critical maintenance and
signal while radio transmitter processes only sound. Lycons
exorbitant price. These problems of the transmitter constitute
(1987) defined radio transmitter as a generator of high
major impediments to individuals and institution that may
frequency electric current whose characteristics of amplitude,
wish to adopt radio broadcast as means of electronic media.
frequency, or phase may be altered or modulated in
The study was therefore carried to design and construct an FM
accordance with the intelligence to be transmitted. Lycons
transmitter that is cheap in price, simple in maintenance,
further adopted the mode of modulation to classify radio
efficient in use yet operate on low power supply. The study
transmitters. In amplitude modulated (AM) transmitter which
was to design and construct a 10 watt FM transmitter to be
is usually employed for broadcast purposes at the medium
received at a range of about 4km in free air. Research and
frequency, the amplitude of a carrier wave is varied in
development (R &D) was used for the study, the necessary
accordance with the amplitude and frequency of modulating
tools and materials were acquired. Design procedure
wave.
involving the modification of an output of a transmitter was
adopted. Based on the procedures adopted and the tests Walter (1987) and Anaemena (2011) observed that frequency
carried out, the specific findings include, appreciable range modulation (FM) transmitter provide greater signal to noise
with stable frequency of transmission obtained on power ratio than amplitude modulated (FM) transmitter for the same
source devised from 12v lead acid battery. Various antenna input. They also highlighted other advantages of FM
instructional applications and mass production strategies were transmitter operating at a very high frequency where noise is
outlined. The successful completion of this study has considerably reduced. In frequency modulation, Anaemena
indicated that practical frequency modulated FM transmitter (2001) maintained that the frequency of the modulated signal
requiring low power can be designed and constructed. Though is constant, therefore, the entire FM system is arranged to be
appreciable range of FM transmitter on low power supply has insensitive to amplitude disturbances. These high scores have
been achieved in this works, further studies in areas of signal created a rapidly growing demand for FM transmitter as a
coupling technique need to be carried to improve the range of means of radio broadcast. FM transmitter is now vigorously
transmission. adopted by state governments that employ it as a means of
radio broadcast for public enlightenment campaigns, news and
educational programmes. FM transmitter has also attracted the
INTRODUCTION interest of tertiary constitute and private individuals that are
attempting to engage in electronic media.
The world has entered an era known as “information age”
when electronics communication systems influence most of Despite its lofty qualities and the rapidly growing desire for
human activities. These electronics communication systems its application in radio broadcast, FM transmitter for practical
consists of three major aspects; the receiver, the channel and broadcast is bedeviled by some of the major problems that
the source, which is the transmitter. A transmitter is an afflict all other transmitters. Walter (1987) complained that
electronics device, which, with the aid of an antenna, the high power supply and high voltage system design are
propagates an electromagnetic signal such as radio, television probably the major problems for any new transmitter type.
or other telecommunications. In the early days, signal energy Safety interlock circuits and warning lights need to be
was generated in transmitting plants using arcs or mechanical employed extensively. Automatic discharge capacitor is
alternators (Farlax, 2005). However, today a transmitter important, otherwise the maintenance or service personnel is

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endangered. Farlex (2005) maintained that transmitter of adopt radio broadcast as means of electronic media. The
larger power requires large current flow with high voltage up private individual and organizations lack resources to
to 20kv. The transmitting plants are also exposed to increased purchase and maintain complex transmitting plant whose price
over voltage risk due to the usually exposed radio tower. is exorbitant and requires critical maintenance. The solution to
this dilemma is the design and construction of FM transmitter
Olaitan (1996) remarked that Nigeria has not contributed
where power supply is derived from low voltage system
significantly to technological development. Against this
which is inherently safe to handle. The present project is
background, the researchers feels that, engineers and others in
design to make use of 12VDC supply, yet produce the range
electronics field in particular take up the challenge to design
as required for local broadcast. If effort is not made to
and construct engineering equipment and gadget that are fee
produce an FM transmitter that is cheap in price, simple in
from such technical problems as afflict radio transmitters.
maintenance, efficient in use and yet operate on low power,
Design as a process can take many forms depending on the individual and private organization may not achieve their
object being designed and the individual participating. Farlex desire in radio broadcast.
(2005) described design as the process of originating and
developing a plan for an aesthetic and functional object,
which usually requires considerable research through METHOD
modeling, interactive adjustment and re-design. Design is also
Design of the study
used both for final plan of action or the result of following
that plan of action (the object produced). According to The design of this study is research and development (R&D).
Longman (1995) design is to make drawing or plan of According to Nworgu (1991) R & D is a process whereby
something that would be built. It is also to develop or plan educational products such as textbooks, equipment, or
something for scientific purpose. The essence of any design is curricular are developed and trial tested in the field to ensure
to build or construct something. Longman further stated that effectiveness. The approach of the design is purely
construction is the process or method of building or making constructional, depicting step-by-step procedure for the
something using many parts. planning and fabrication of products and gadgets.
This study is a design and construction project conceived to
Materials and tools
produce an FM transmitter free from the major technical
problems highlighted, but of appreciable range for practical The materials and tools that were used for the design and
application. The design of this FM transmitter will construction of FM transmitter include: copper laminate plate
incorporate, at the output stage, the very high frequency Gross paint (Resis), Nitric acid menthylene chloride,
(VHF) power transistor no 2c 1971 (NTE343) which has detergently electric technician knife, soldering iron (40-watts)
produced excellent results in other circuits. alloy lead, file halksaw pliers, etc.

Statement of the Problem Components

A rapidly growing demand for the use of FM transmitter The various components to be used for each part of the project
exists among individuals and institutions. For example are listed. To facilitate adequate understanding of their
universities and other tertiary institutions need to broadcast operations the major components in this circuit with respects
educational, entertainment and even news programme that are to the characteristics were discussed.
particularly designed for campus audience. Franco FM is an
FM transmitter attempting to satisfy this need in university of s/n Component description Specification
Nigeria, Nsukka. Private individual also wish to provide a 1 Resistor R1 22k
view of local and community news that is independent
government stand. These plants are however complex 2 Resistor R2 100k
equipment demanding high power supply, high voltage
3 Resistor R3 1k
system design, critical maintenance and exorbitant price.
Farlex (2005) stated that transmitters of large powers require 4 Resistor R4 100
large current flow with high voltage up to 20kiv and
transmitting plants are exposed to increased over voltage risk 5 Resistor R5 390
due to the usually exposed tower. Walter (1987) complained 6 Resistor R6 330
that the power supply and high voltage system design are
probably the major problems for any new transmitter type. 7 Resistor R7 1k
These problems of the transmitter constitute major 8 Resistor R8 100
impediments to individual and institution that may wish to

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9 Resistor R9 1k Design procedure

The design procedure for the project hinged on an existing
10 Resistor R10 15
frequency modulated (FM) transmitter circuit. This transmitter
11 Resistor R11 10k circuit, which the researchers constructed and tested, exhibited
some desirable characteristics that qualiofied it as a base for
12 Resistor C1 1n further design. Operating efficiently on a low-power 12 vdc
13 Resistor C2 100n which process minimal safety problem, the transmitter
produced sound output with optimum signal-noise ratio (SNR)
14 Resistor C3 1n and high fidelity comparable to practice broadcast transmitter.
15 Resistor C4 47pf However, the transmitter incorporates a low power (250mw)
output stage using transistor 2N2369 which produces a range
16 Resistor C5 10pf too short for practical application. The design procedure then
involved the calculations experiments and exercises required
17 Resistor C6 100uf/25ve
to successfully replace the low output of the existing
18 Resistor C7 100pf transmitter with medium output stage of useful broadcast
value. The output stage of the existing transmitter starting
19 Resistor C8 47pf from C9 to BALLUN was cut off as shown in fig. 3b and
20 Resistor C9 47pf replaced with a specially designed medium power output
stage consisting of VHF NTR 342 transistor circuit.
21 Resistor C10 1n

22 Resistor C11 10pf

Design calculation
23 Resistor C12 3 pf Design calculation
24 Transistor Q1 Bc 548 For stage 1 (Q1);
25 Transistor Q2 Bc 548 Applying Kirchoff’s voltage law to the base side and taking
resistance in K and current in MA we have.
26 Transistor Q3 Bc 548
Vcc = IBRB + VBE + RE X IE
2 Transistor Q4 NTE 342 or 2c1971
12v = 1b X RB + O + RE x 1E (Neglecting VBE)
28 Inductor L3 Turns 22 swg
12 = 100 x 1B x IB + IE x 1
29 Balunl Transformer
12 = 100IB + (IC + IB)
30 Feeder wire 300 TV feeder
12 = 100IB + (00IB + IB) for β = 100
31 Antenna Dipole 12 = 00IB + 101 IB
32 JPI to JP5 Jumper wire 12 = 201IB
33 Balunl wire Jumper wire
Fabrication of Printed circuit board
The fabrication process of the printed circuit board starts from
Modified output stage screening/filming. The folwing materials were used at the
screening stage; steizer, emulsion transparent glass, hard
S/n Component description Specification
book, foam water mesh (silk) and sun light. The following
34 Capacitor 13/14 22 pf sequence were carefully followed to ensure quality transfer of
the master printed circuit pattern to the copper side surface.
35 Capacitor 14 120 pf ceremanic

36 Capacitor 15 22 pf ceramic Procedure

(1) Mixture: Steier and emultion were mixed and poured on
37 Capacitor 16 39 pf ceramic
the mesh (silk). A smooth piece of plastic was used to rub
38 Coil Coil the mixture repeatedly on the silk until the mixture had
vanished on this side. The mixture then reappeared on the
39 Resistor Choice
opposite side, and turning tot hat side, and using the
plastic material the mixture ran gently along this side

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until it vanishes and reappeared at the initial side. The Drilling of Holes
process of turning and rubbing stopped when the mixture
Holes were drilled to produce openings through the printed
was completely absorbed and could not significantly
circuit board in order to form electric connections between
appear on either side.
conducting pathways. The holes were drilled in such ways
When the mixture disappeared from either side, the silk was than only one conductor’s lead or wire passes through.
allowed to dry thoroughly for about 30 minutes. The
Reference designation: Components generally were inserted
terms coating and curling are used to describe the
opposite copper side so that their terminals would not bridge
vanishing and reappearing of the mixture at both sides of
or short circuit. To show the position each component enters;
the mesh. It was done under a shade so that light rays did
reference designation was drawn opposite copper surface to
it fall on it.
correspond with the circuitry opposite.
(2) Screening: The film (the bold black master print pattern)
Component layout: The design of electronic circuit wiring
was be placed on the silk. The transparent glass,
takes into account, most importantly, component placement,
rectangular in shape, was placed under the silk directly
wiring density and the functional performance of the entire
opposite the film. The entire arrangement constitutes the
system the parts and component of this design were carefully
assembly. The assembly was brought to reach the degree
spaced to provide even diagram balance between blank spaces
of polymerization was dependent on the light intensity.
and lines. Enough spaces were left in the area near symbol to
(3) Dispatch: After the thirty seconds count to the sun was avoid crowding of reference information.
certified, the assembly was carefully returned to the shade
Resistor diodes, transistors and capacitor were inserted into
and dispatched (de coupled).
their reference designation using terminal and polarity
(4) Developing: After de-coupling the assembly, a foam was identification techniques. All components were mounted
dipped into clean water and squeezed into the mesh approximately 5mm above the panel and excess leads of wires
repeatedly for three minutes. The foam was gently rubbed were cut to about 2mm above the copper side surface. The
on the silk so that a bright white line of the pattern cutting or trimming of the excess leads was done after
showed up. soldering has been completed.
(5) Having ascertain the appearance of the film (on the silk) The researcher must take certain precautions when inserting
water was poured continuously on both sides of the silk. components into holes. These precautions according to Cole
After a while the foam was rubbed on the wetted side, (1988) include:
and the appearance of the pattern increased. This
1) Mastery of resistors colour codes to ensure that the
recycling event continued until the entire printed circuit
desired values of resistors will be fitted to their correct
diagrammatic pattern was fully cured the silk was
reference designation.
allowed to dry completely.
2) Mastery of non-electrolytic colour coded capacitors in
(6) When the mesh had completely dried, a proportionate
order to be able to interpret the decimal numbers.
amount of ink called sticker ink was poured on the coated
side of the mesh. The resist coated copper surface was 3) Ensure that transistors are fitted correctly.
placed opposite directly under the coated csilk on a flat
4) Mount the power transistors on heat sink. The function
surface. The ink was run evenly along the silk with
of the heat sink is to remove dissipated heat from the
plastic materials, then the diagrammatic pattern appeared
transistors to avoid thermal run away.
unto the resist copper side and the silk was removed to
dry the board completely. Initially the copper side surface 5) Note the position of the pins and sign for the ICS.
was coated with a gray coloured resist material. An Soldering procedure: Every component inserted on the
electricians knife was used to remove to the resist printed circuit board PCB were carefully and neatly soldered
material from areas not covered with the conductor to avoid being pulled out. The soldering iron was allowed to
routing imaged pattern. heat properly to ensure quick melting of the alloy (60/40)
(7) Finally, the board was thoroughly washed with detergent lead. A 40 watt soldering iron was used to avid overheating
and rinsed with much water then allowed to dry the components. Soft soldering was used because it is more
completely. It was then ready for etching. suitable for light points in steel, copper, brass and electronics
works. It is not used were much strength is required or in
Removing resist: The purpose of the resist coating is to
cases where the point will be subjected to vibrations or heat,
prevent the circuit pattern on the board from being removed
as the solder is comparatively weak and has low melting point
by the nitric acid. The resist will be completely removed from
(Chapman, 1988).
the surface easily and quickly by applying methylence
chloride solution.

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Casing (Cabinet) Construction used to mark out the layout tracks unto the surface of the
board. The result is neat and precise artwork which, when
Several materials can be used for constructing the case of an
etched gives very professional finish.
FM transmitter both for commercial and instructional
purposes, but sheet metal was adopted for this project. The first step in process of etch-resist transfer is
screening/firming. The following materials were used at this
Technical and aesthetic consideration guided the choice of
stage, - seteier, emulsion, transparent glass, hard book, foam
material for the cabinet. Since the production of electronic
water, mesh silk and sunlight. The following sequence was
systems demand the application of different kinds of primary
carefully applied to assure quality transfer of the master
inputs a skilled sheet metal technicians at Government to
printed circuit pattern to the copper surface. Seteizer and
science technical college Abuja produced the cabinet. The
emulsion were mixed and poured on the silk. A smooth flat
researchers however, submitted the specification (250 x 200 x
piece of plastic was used to rub the mixture repeatedly on the
150).
silk until the mixture had vanished from this side.
Testing techniques The mixture reappeared on the opposite side and turning that
side and using the material, the mixture was run gently along
Every new assembly requires testing before it can be
this side until it vanished and reappeared at the initial side.
connected to the power supply in order to ensure that it will
The process of turning and rubbing was stopped when the
function correctly and safely (IEE Regulation, 1988).
mixture was completely absorbed and could not significantly
1. The following tests were carried out on this device. appear on either side. After coating and curling (vanishing and
2. Continuity test is required to detect all section that reappearing of the mixture) the silk was allowed to dry
have open circuits. thoroughly for thirty (30) minutes.
3. Polarity test is required to ensure that every live In the screening, the film was placed on the silk. The
terminals are done in such a way that there is no transparent glass, rectangular in shape was placed over the
bridge between the terminals. film, and the hard book was placed under the silk directly
In this chapter, the required tools and materials have been opposite the film. The entire arrangement known as assembly
presented. The components have been listed with the design was then brought under sun light for the film exposure. The
calculations of some of these component carried out to exposure time required to reach the degree of polymerization
ascertain their performances in the circuit. The fabrication ahs was dependent on the light intensity.
been explained with emphasis on printed circuit board and After the exposure the assembly was decoupled ready for
soldering techniques. developing. In developing, a foam was dipped into clean
water and squeezed unto the mesh repeatedly for three
Fabrication and testing seconds. The foam was gently rubbed on the silk so that a
In this chapter, the description of the procedures leading to the bright white line of the pattern shown up. Having ascertained
construction of an FM transmitter is given. Brief explanation the appearance of the film, water, was poured continuously on
on the manufacture of printed circuit board starting from both sides of the silk. After a while the foam was rubbed on
circuit diagrammatic pattern (artwork) to etching has been the wet side to increase the appearance of the pattern. This
presented. Many testing procedures required for effective recycling event continued until the entire printed circuit
operation of this project beginning from continuity test to diagrammatic pattern was fully cured. The silk was allowed to
transmitter range test have been outlined. dry completely.
When the mesh had completely dried, a proportionate amount
Printed circuit board of ink called sticker ink was poured on the coated side of the
Of all the construction steps that this project demand, printed mesh. The resist copper surface was placed opposite directly
circuit board required the greatest amount of thinking and skill under the coated skill on flat surface. The ink was ran evenly
in its preparation. Small-scale production can be achieved by along the silk with the plastic material, then the diagrammatic
following the procedures outlined. pattern appeared unto the resist copper side. Then the silk was
removed and the copper side surface was dried completely.
To produce the layout diagram and the pcb artwork is perhaps Copper resist was removed from surplus copper with
the most difficult of this method of construction. The electrician knives. Finally, the board was thoroughly washed
development of the template for the printed bard was achieved with detergent and dried ready for etching. Etching is the
through series of careful design of electrical circuit. process of removing excess copper from the board. Nitric acid
Several methods are used to transfer the artwork onto the was used because it dissolves copper quickly.
surface of the board for example etch-resist pen, etch resist
transfers and photographic method. Etch resist transfers is

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Component designation fault that it did not fall. Soldering is one important factor in
electronics systems design which if poorly done can
Component designation fault existed on the circuit as shown
undermine the operation of the system. Therefore, the
in the diagram and thus lead to wrong positioning of the
soldering processing was carried carefully to ensure good
component.
system performance.
Component designation
Transistor Testing
Component designation faults with respect to transistor Q 2
When constructing this FM transmitter testing was carried out
and Q2 existed on the circuit as shown in fig 4 and this lead to
on the transistors before, they were soldered on the printed
wrong positioning of the two transistors on the printed circuit
circuit board. The conditions of the transistors needed to be
board. According to this component designation fault, the
verified because brand transistor like any other semi-
population process swapped the collector and emitter
conductor device could be faulty from the shelf. Many
terminals of these transistors. As a result, these transistors
techniques technologist and engineers have complained that
were wrongly biased in such a way that their emitters were at
the new ic or transistor that they had fitted into a circuit was
the highest potential followed by their base with the collectors
faulty. With the transistor out of the circuit, the two-diode
at the lowest potentials. The emitter/base junctions were
junctions of the transistors were checked with digital
reverse biased while collector/base functions were forward
multimeter. For an NPN transistor, the test was as follows:
biased causing very poor system performance. This was
the positive lead of the ohmmeter was connected to the base
against the conventional biasing mode which is emitter/base
and the negative (common) lead was connected to the emitter.
junction forward biased, and collector based junction reverse
This forward biased the base/emitter junction, and the
biased for NPN transistor.
ohmmeter recorded low reading. The negative terminal was
then connected to the collector. This forward biased the
Soldering
base/collector junction and the ohmmeter recorded low
Soldering exercise carried out with 40watt soldering iron was reading. Then the ohmmeter reverse biased the two junction
performed with due regard to safety. Before starting to solder and both junctions read high. If one of the junctions read low
the bit of the soldering iron was cleaned when hot by wiping it in both conditions the junctions was shorted. If ohmmeter
across a wet sponge or fine abrasive paper. Melting some recorded high reading in both reverse and forward bias
solder onto the bit (known as tinning) and wiping that off in condition then the junction was open circuit and the transistor
the sponge helps this cleaning process as solder contains cores was bad.
of flux, which is a cleaning agent.
Next, reading was made between the collector and emitter, the
For a successful result, all parts of the board to be soldered meter leads were reverse to make a second reading. Both of
were dry and free from dirt and grease. A hot soldering iron these readings should be high. If not, the transistor had a
was used to produce good solder joints. The joints were made collector emitter junction short circuit short and was replaced.
hot but not too hot to overheat it as overheating can cause If the terminals were unknown, the base terminal was found
damage. The soldering iron was placed so that it was touching by identifying which had a low reading in relation to the other
both the lead to be soldered and the copper track to which it two terminals. This terminal was the base. If the low readings
was to be joined. After a few-seconds the solder was applied were caused by the base being positive, the transistor was
to the track to melt and flow up around the base of lead NPN. If the low readings were caused by base being negative,
forming a wedge. Solder flow cold to hot and therefore if the transistor was PNP.
either the lead or track was cold, solder would not flow and
dry which would result. According to Kavacs (1989), a dry Continuity Test
joint is one which has failed to bond sufficiently strongly with
When all the components had been soldered on the printed
the copper track and as a result it provides a poor conducting
circuit board (PCB) continuity test was carried out before the
path for current. The dry joints were put right by applying a
connecting the system to power supply. The test revealed
clean soldering iron to the joint and leaving it long enough for
open circuit faults, which could be due to:
it to melt the solder so that it flows properly.
1. A break in the circuit.
Apart from dry joints another problem encountered in the
soldering was solder bridges linking tracks. This happened 2. The failure of a component leading to it having an
when too much solder was applied to the joint and an adjacent unusually high resistance or.
track was heated at the same time as the joint, perhaps by
3. An increase in the insulation at certain points caused
using a soldering iron bit which was too large. The situation
by dirt, grease or corrosion.
was dealt with immediately as it occurred. Solder sucker was
used to remove the hot solder. Any component that has been 4. It also revealed that short circuit faults which were
picked and placed in the hole was soldered immediately so due to;

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5. The failure of a component leading to it having an However, with the microphone feed resistor R1 removed the
abnormally low resistance. circuit has been operating efficiently with omni-directional
dynamic microphone without any damage. The circuit in this
6. The touching of uninsulated parts of the component
condition neither worked nor burnt the unidirectional
terminal
microphone.
7. The effects of moisture lying between conducting
paths which create links of lower resistance than the Transmitter Range Testing
component or.
Transmitter range testing involved the process required to
8. Solder bridges between the terminals. determine the distance from transmitter its signal will be
received. This test required a radio receiver with FM band, a
Static test
cassette player or an assistant producing direct audio that will
As soon as this project was connected to power supply, the be feed into the microphone. The test also requires an antenna
static test involving transistor terminal voltage readings was installation described below. The transmitter, cassette player
carried out before AC signal was injected into the circuit. A and radio receiver were switched on simultaneously. The
tpical static test for transistor Q1 was as follows. radio receiver set to FM band was tuned gradually to capture
the main frequency then moved away from the transmitter to
VC Collector voltage with respect to region = 8v
the farthest point signal could be received.
VB base voltage with respect to ground = 1.7v
Ballun
VE emitter voltage with respect to ground = 1.0
Balanced and unbalanced transformer is necessary because the
In addition to the biasing conditions, the static test also
output of this FM transmitter is an unbalanced impendence of
revealed faults such as open circuit and short circuits in
transistors and other semi-conductor components. 75 which is to be coupled to an antenna of 300 impendence
 (Patric 2003). The BALLUN a 1:4 balanced and
Power supply unbalanced transformer, is therefore required for efficient
coupling. All the coaxial cable joints to the transmitter and
The process of construction and testing of this project showed BALLUN were carefully made to avoid short circuit or open
that the most suitable power supply for the efficient operation circuit faults that will undermine the performance of this
of this transmitter is the 12 volt lead acid battery. This source transmitter.
of power supply is completely free from AC ripples that cause
electrical noise especially in oscillation circuits. An
alternative source of power supply is the highly regulated and CONCLUSION
efficiently filtered power pack circuit which is costly.
So, far the test result of this project which is the outcome of
The circuit for this project consists of track-etched inductor construction procedures has revealed the successful
whose reactance is determined by voltage level. Any change achievement of the primary objective; the design and
in this voltage level as a result of ripples or fluctuations construction of an FM transmitter of appreciable range
existing in the power supply is converted to equipment operating on 12v power supply. Because of the impressive
change in the inductive reactance. This change in inductive good result, obtained from the usability test, the FM
reactance is converted by the circuit to variation or drift in transmitter is now ready for either instructional or
oscillation frequency of the transmitter. In the initial test, entrepreneur purposes. The successful completion of this
when the transmitter was connected to ordinary 12v power study has indicated that practical FM transmitter requiring low
supply consisting of transformer rectifier and filter circuit, its power input can be designed and constructed.
output was seriously affected by frequency drift and electrical
noise.
RECOMMENDATIONS
Microphone connection
In view of the handicap suffered by the researchers in effort to
Microphone converts sound energy to electrical energy for conduct this project successfully, and the general findings, the
further processing by the circuit. In this project, the following recommendations are hereby made.
microphone is connected to coupling compactor C1 to feed
modulating signal to the base of the transistor Q1. With the 1. Students of Industrial Technical Educational and
microphone feed resistor R1 retained, the circuit worked with other related technical programs should be
only undirectional microphones many of which were burnt encouraged to undertake design and construction
each within a few hours of usage. The circuit only burnt but projects to enhance the technological development of
did not work with omni-directional dynamic microphone. Nigeria.

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2. The electrical/electronics section of the Vocational

Teacher Education Department, University of
Nigeria Nsukka should be provided with functional
materials and equipment especially in areas of test
and instrumentation. These will be of vital
importance to the students’ training and project work
activities.

REFERENCES
[1] Brindly, K. (1987). Radio and electronic engineers
pocket book. London: Heinemann Ltd.
[2] Chapman, W.A.J. (1988). Workshop technology part 1.
London: Arnold International Students Ed.
[3] Cole, I. W. (1988). Foundations (ICE Works
construction guides). London: Thomas Telford.
[4] Farex, L. (2005). Transmitter-encyclopedia articles
about transmitters. http:wysiwgy:118/file:al;transmitter.
Accessed 7/4/2005.
[5] Institute of Electronic Engineering IEE regulation,
(1985). London: Savah Place Publishing Coy.
[6] Lycos, L. (1980). Radio communication laboratory –
built for transmitters
http://memberstroipor.com/rclindia/trans.html. accessed
on 5/3/2005.
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