Select Currency
Translate this page

THE DESIGN & CONSTRUCTION OF MINI RADIO BROADCAST TRANSMITTER AND AUDIO CONSOLE USING FREQUENCY MODULATION (FM) WITH POWER RATING OF 1 WATT

Format: MS WORD  |  Chapter: 1-5  |  Pages: 87  |  949 Users found this project useful  |  Price NGN3,000

  DOWNLOAD THE FULL PROJECT

ABSTRACT

The early transmitter for radio broadcasting is so big and bulky that they do occupy numerous spaces. The circuitries are mainly designed with valves, which are big in sizes. With the advent of semiconductor materials such as transistors electronic equipment are now becoming miniaturized such that small transmitters are now becoming handy and compact. In line with this we choose to design a complete radio broadcasting equipment tat is compact and existence of semiconductor materials. The system units are of two categories namely: audio console for the processing and mixing of musicals is basically a condenser microphone. The transmitter unit is where the center frequency is provided. All these were designed to be in compact and small manner. This project is aimed at serving a community using a small and compact radio broadcasting equipment with a power watt of 1 watt a community of 1 kilometer in radius should be covered comfortable and the audio production very clear unlike the common noisy FM microphone project.

 

CHAPTER ONE

INTRODUCTION

This our project work is all about design and construction of a complete radio broadcasting equipment that is compact and miniaturized. It is capable of delivering a power output of 1 watt and assumed to cover a distance of 400 meters ie 200 meters radius depending on obstructions. The transmitted signal is frequency modulated stays constant and its frequency varies according to the amplitude variations of the audio signal. When the input signals amplitude increases (ie during the positive half cycle) the frequency of the carrier increases too, on the other hand when the input signal decreases in amplitude (negative half-cycle or no signal) the carrier frequency decreases accordingly.

The output frequency of the transmitter is adjustable from 88 to 108 MHZ, which is the FM band that is used for radio broadcasting. The circuit as we have already mentioned consist of four stages. Three RF stages and one audio preamplifier for the modulation. The first RF stage is an oscillator is controlled by LC network L-C, C is there to ensure that the circuit continues oscillating and C adjusts the coupling between the oscillator and the next RF stage which is an amplifier. This is built around TR2 which operates in clas c and is tuned by means of L and C. the last RF stage is also an amplifier built around TR3 which operates in class c the input of which is tuned by means of c and l. From the output of this last stage which is tuned by means of l-c is taken then the output signal which through the tune circuit l-c goes to the aerial.

The circuit of the preamplifier is very simple and is built around TR4. The input sensitivity of the stage is adjustable in order to make it possible to use the transmitter wit different input signals and depends upon the setting of VRI. As it is the transmitter can be modulated directly with a piezoelectric microphone, a small cassette recorder etc. it is of course possible to use an audio mixer in the input for more professional results which we did

CHAPTER ONE

TRANSMITTER FUNDAMENTAL AND TYPES OF MODULATION

1.1  TRANSMITTER FUNDAMENTALS

The AM transmitter generates such high power that it’s prime requirement is efficiency. Amplitude modulation can be generated at any point after the radio frequency source as a matter of fact, even a crystal oscillator could be amplitude modulated except that this would be an unnecessary interference with its frequency stability. If the output stage in a transmitter is plate modulated the system is called high-level modulation. An AM transmitter which may be either low level or high level modulated have a stable RF source and buffer amplifier followed by RF power amplifier.

The audio voltage is processed or filtered so as to occupy the correct bandwidth and compressed somewhat of reduce the ration of maximum to minimum amplitude. In IM transmitter, the prime requirement of an FM system is a variable output frequency, with the variation proportional to the instantaneous amplitude or the modulation voltage. The power and auxiliary stages of FM transmitter are similar to those in AM transmitter except that FM has an advantage, since it is a constant amplitude modulation system all the power amplifier can be operated in class c and that is very efficient.

1.2   MODULATION (ANALOG AND DIGITAL

Modulation is the systematic transformation of a carrier wave in accordance with the message signal. To a large extent the success of a communication system in any given mission depends on the modulation so much so that the type of modulation is a pivotal decision to system design. There are two basic types of modulating techniques the analog and digital modulation. Analogue modulation uses sinusoidal waveform as the carrier signal while digital modulation uses a discrete or pulse train as the carrier signal. Analogue modulation being a continuous process is obviously suited to signal that are continually varying with time. The carriers are at a frequency much higher modulating signal. The modulation process is thus characterized by frequency translation. Pulse modulation is discontinuous or discrete process in the sense that the pulses are present only at a certain interval of time. In the past, analogue modulation methods have been very largely exploited and still are because of the capital investment in existing systems and theirs basic simplify. The two most important methods of analogue modulation are amplitude modulation.

1.3       AMPLITUDE MODULATION (AM).

In amplitude modulation the amplitude of a carrier the modulating voltage whose frequency is invariably lower than that of the carrier varies signal. AM is defined as a system of modulation in which the amplitude of the carrier is made proportional to the instantaneous amplitude of the modulating voltage. Let the carrier voltage and the modulating voltage Vc and Vm respectively be represented by

Vc = VC Sin Wct

Vm = Vm Sin Wmt

Note that phase angle has been ignored in both expressions since it is unchanged by the amplitude modulation process from the definition of AIG amplitude vc. Of the unmodulated carrier will have to be made proportion to the instantaneous modulating voltage vm sin wmt where the carrier is amplitude modulated.

1.4       FREQUENCY MODULATION

Frequency modulation is a system in which the amplitude of the carrier is made constant whereas its frequency is varied about its unmodulated frequency in a way and manner determined by the amplitude of the modulating signal. When the information signal is positive the carrier frequency is increased above its unmodulated value. The increase in carrier frequency varies linearly with the instantaneous value of the information reaching a maximum when the modulating signal reaches its peak value. The converse applies when the modulating signals is negative ie the instantaneous carrier. Frequency being decreased in proportion to the instantaneous value the modulating or information signal.

The illustration is shown below

Modulating signal

V

0  Fig 1.4a

Carrier signal

V

0  Fig 1.4b

V                                                                                                Frequency modulated signal Fig 1.4c

1.5      METHOD OF FREQUENCY MODULATION

There are two methods namely direct and indirect. In direct method, frequency modulation is obtained by varying the frequency of an oscillator. If either the capacitance or inductance of an L C oscillator tank is varied FM of some form will result and is the variation is made directly proportional to the voltage supplied by the modulation circuits true FM will be obtained. The direct modulator has the disadvantages of being based on an LC oscillator which is not stable enough for broadcast purposes. And if the variation is made directly proportional to the voltage supplied by the modulation circuits true FM will be obtained. The direct modulators have the disadvantages of being based on an LV oscillator, which is not stable enough for broadcast purpose. This requires stabilization of the modulator with attendant circuit complexity: this method is called INDIRECT METHOD.

 1.6      MODULATOR OVERVIEW

Of the various methods of providing a voltage variable reactions which can be connected across the tank circuits of an oscillator the most common are the reactance modulator and vibratory diode. These will now be discussed as below:

1.61     BASIC REACTANCE MODULATOR

Provide that certain simple condition are met, the impedance Z as seen at the input terminal A-A of figure is almost entirely reactive. The circuit shown is the basic circuit of FET reactance modulator which behaves as a three- terminal reactance that may be connected across the tank circuit of the oscillator to be frequency modulated. It can be made inductive or capacitive by a simple component change. The value of this reactance is proportional to the Tran conductance of the device, which can be made to depend on the gate bias and its variations

1.62     THEORY OF REACTION MODULATOR

In order to determine Z, a voltage V is applied to the terminals A-A between which the impedance is to be measured, and the resulting current i is calculated. The applied voltage is then divided by this current giving the impedance seen when looking into the terminals. In order for this impedance to be a pure reactance (it is capacitive here). Two requirements must be fulfilled.

 ib

Vg

Basic reactance  

Modurator circuit       

The first is that the bias network current ib must be negligible compared to the drain current. The impedance of the bias network must be large enough to be ignored. The second requirement is that the drain – to- gate impedance (Xc here) must be greater than the gate to source impedance (R in this case) preferably by more than 5:1. the following analysis may then be applied.

Vg = ibR = RV

R-jXc

FET drain current is

i = gmVg = gmRv

                        R-jXc

:. Impedance at A – A

Z          = V = V – gmRv R – jXc

i R-jXc gmR

            = I . (I jXc)

gm R

Z = -j Xc

gmR

X eq = Xc = I  I .

gmR 2P fgmRC = 2P Fceq

Ceq = gmRc

Xc = 1

Wc = nR

Ceq = gmRc = gmR

            2Õ FnR

ceq = gm

2Õ Fn

1.7      TYPES OF REACTANCE MODULATOR

There are four different arrangement of the reactance modulator (including the one initially discussed), which will yield useful results. Their data are shown in table below. The general prerequisite for all of them is that drain current must be much greater than bias network current. It is seen that two of the arrangement gave a capacitive reactance and the other two gave an inductive reactance. In the reactance modulator shown below an RC capacitive transistor reactance modulator, quite a common one in use operates on the tank circuit of a clap -Gouriet oscillator. Provided that the correct component values are employed any reactance modulator may be connected across the tank circuit of any LC oscillator (not crystal) with one provision. The oscillator used must not be one that requires two tuned circuits for its operation such as the tuned-base tuned- collector oscillator. The hartly and copitts (or clap-Gouriet) oscillators are most commonly used and each should be isolated with a buffer. RF chokes in the circuit shown are used to isolate various points of the circuit for alternating current while still providing a dc path.

TABLE 1.7 reactance modulator elements

NAME Zgd Zgs Condition Reactance Formula A

RC Capacitive

C

R

Xc> > R

Ceq =gmRC

RC Inductive

R

C

R> > Xc

Leq =RC

gm

RL Iductive

L

R

XL > >R

Leq = L

gmR

RL Capacitive

R

L

R> > XL

Ceq = gmL

R

1.8       VARACTOR DIODE MODULATOR

A varactor diode is a semiconductor diode whose junction capacitance varies linearly with the applied voltage when the diode is reverse biased. It may also be used to produce frequency modulation. Varactor diode is certainly employed frequently, together with a reactance modulator to provide automatic frequency correction for an FM transmitter. The circuit below shows such a modulator. It is seen that the diode has been back biased to provide the junction capacitance effect and since this bias is varied by the modulating voltage which is in series with it, the junction capacitance will also vary, causing the oscillator frequency to change accordingly. Although this is the simplest reactance modulator circuit. It does have the disadvantage of using a two terminal device, its applications are some what limited. However it is other used for automatic frequency control and remote turning.

To oscillator           

Cb (Rf)  AF in

Varactor

diode

fig 1.8   Varactor diode modulator    Vb

  DOWNLOAD THE FULL PROJECT

Not What You Are Looking For?



For Quick Help Chat with Us Now!

+234 814 010 7220

+233 541 351 187


Here's what our amazing customers are saying

Emmanuel Essential
Kogi state University
I actually took the risk,you know first time stuff But i was suprised i received as requested. I love you guys 🌟 🌟 🌟 🌟
Very Good
Azeez Abiodun
Moshood Abiola polytechnic
I actually googled and saw about iproject master, copied the number and contacted them through WhatsApp to ask for the availability of the material and to my luck they have it. So there was a delay with the project due to the covid19 pandemic. I was really scared before making the payment cause I’ve been scammed twice, they attended so well to me and that made me trust the process and made the payment and provided them with proof, I got my material in less than 10minutes
Very Good
Gbadamosi Solomon Oluwabunmi
Lasu
Swift delivery within 9 minutes of payment. Thank you project master
Excellent
JONNAH EHIS
Ajayi Crowther University, Oyo
I was scared at first when I saw your website but I decided to risk my last 3k and surprisingly I got my complete project in my email box instantly. This is so nice!!!
Excellent
MATTHEW NGBEDE
Ahmadu Bello University
I wish I knew you guys when I wrote my first degree project, it took so much time and effort then. Now, with just a click of a button, I got my complete project in less than 15 minutes. You guys are too amazing!
Excellent
Temitayo Ayodele
Obafemi Awolowo University
My friend told me about iprojectmaster website, I doubted her until I saw her download her full project instantly, I tried mine too and got it instantly, right now, am telling everyone in my school about iprojectmaster.com, no one has to suffer any more writing their project. Thank you for making life easy for me and my fellow students... Keep up the good work
Very Good
Stancy M
Abia State University, Uturu
I did not see my project topic on your website so I decided to call your customer care number, the attention I got was epic! I got help from the beginning to the end of my project in just 3 days, they even taught me how to defend my project and I got a 'B' at the end. Thank you so much iprojectmaster, infact, I owe my graduating well today to you guys...
Excellent
Ibrahim Muhammad Muhammad
Usmanu danfodiyo university, sokoto
It's a site that give researcher student's to gain access work,easier,affordable and understandable. I appreciate the iproject master teams for making my project work fast and available .I will surely,recommend this site to my friends.thanks a lot..!
Excellent
Dau Mohammed Kabiru
Kaduna State College of Education Gidan Waya
This is my first time..Your service is superb. But because I was pressed for time, I became jittery when I did not receive feedbackd. I will do more business with you and I will recommend you to my friends. Thank you.
Very Good
Joseph M. Yohanna
Thanks a lot, am really grateful and will surely tell my friends about your website.
Excellent

HOW TO GET YOUR COMPLETE PROJECT INSTANTLY

  • Select 3 Project Topics of your choice from your Department.
  • Submit the 3 topics to your Supervisor for Approval.
  • Call Our Instant Help Desk on +234 814 010 7220 and Get Your Complete Project Material Instantly.
  • All project materials on this website are well researched by professionals with high level of professionalism.

FREQUENTLY ASKED QUESTIONS

How do i choose a Project Topic?

Look for your department and select any topic of your choice

I have a fresh topic that is not on your website. How do I go about it?

How fast can i get a complete project from your website?

Within 15 minutes if the exact project topic is on our website

Is it a complete research project or just materials?

It is a Complete Research Project i.e Chapters 1-5, Abstract, Table of Contents, Full References, Questionnaires / Secondary Data

One of your topics suites my project, but the case study is different. What do i do?

Call Our Instant Help Desk Now: +234 814 010 7220 and you will be responded to immediately

How do i get my complete project?

Your Complete Project Material will be sent to your Email Address in Ms Word document format

Can I get my Complete Project through WhatsApp?

Yes! We can send your Complete Research Project to your WhatsApp Number

What if my Project Supervisor made some changes to a topic i picked from your website?

Call Our Instant Help Desk Now: +234 814 010 7220 and you will be responded to immediately

Do you assist students with Assignment and Project Proposal?

Yes! Call Our Instant Help Desk Now: +234 814 010 7220 and you will be responded to immediately

What if i do not have any project topic idea at all?

Smiles! We've Got You Covered. Chat with us on WhatsApp Now to Get Instant Help: +234 814 010 7220

How can i trust this site?

We are well aware of fraudulent activities that have been happening on the internet. It is regrettable, but hopefully declining. However, we wish to reinstate to our esteemed clients that we are genuine and duly registered with the Corporate Affairs Commission as "PRIMEDGE TECHNOLOGY". This site runs on Secure Sockets Layer (SSL), therefore all transactions on this site are HIGHLY secure and safe!