Fm Radio Transmitter

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  • Topic: Radio, Capacitor, RLC circuit
  • Pages : 6 (1774 words )
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  • Published : April 25, 2012
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2012
A SYNOPSIS ON

SUBMITTED BY:
RAJ KUMAR DHAKAD
BRIJESH PATEL
RAJEEV KIRAR
RASHMI RAI

FM RADIO TRANSMITTER

ACKNOWLEDGEMENT
Practical knowledge means the visualization of the knowledge, which we read in books. For this we perform experiments & get observation. Practical knowledge is very important in field. One must be familiar with the problems related to the field so that he may solve them and becomes successful person. After achieving proper goal of life an engineer has to enter in the professional life. According to this life he has to serve an industry, may be public or private sector or self own. for the efficient working in the industry, labors problem etc, so he can tackle them successfully.

S.NO.| CONTENTS| PAGE NO.|
1| CIRTIFICATE| II|
2| ACKNOWLEDGEMENT| III|
3| LIST OF SYMBOLS| IV|
4| LIST OF FIGURES| IV|
5| LIST OF TABLES| IV|
6| ABSTRACT| 1|
7| INTRODUCTION| 1|
8| FM TRANSMITTER CIRCUIT DISCRIPTION| 2|
9| ASSEMBLY INSTRUCTION| |
10| CIRCUIT CALLIBRATION| |
11| LEARNING EXPERIENCE| |
12| LIST OF COMPONENTS| |
13| CONCLUSION| |
14| APPENDIX| |
15| FUTURE PROSPECTS & INNOVATIONS| |
16| REFERENCES| |

LIST OF SYMBOLS
1. L INDUCTANCE
2. R RESISTANCE
3. C CAPACITANCE
4. V VOLTAGE
LIST OF FIGURES
1. Figure 3.1:Fm transmitter circuit design
2. Figure 5.1:

LIST OF TABLES
1. Table 1: List of components

ABSTRACT
This project explains the design and construction of a simple FM transmitter. The transmitter is made from identical discrete bipolar junction transistors. Continuous tuning is achieved with a variable capacitor. The designed tuning range was 88MHz to 108MHz. The transmitter can transmit audio signal on a 91.7MHz carrier over a distance of 300meters in open air.

INTRODUCTION

Frequency modulation (FM) is a technique for wireless transmission of information where the frequency of a high frequency carrier is changed in proportion to message signal which contains the information. FM was invented and developed by Edwin Armstrong in the 1920’s and 30’s. Frequency modulation was demonstrated to the Federal Communications Commission (FCC) for the first time in 1940, and the first commercial FM radio station began broadcasting in 1945. FM is not a new concept. However, the concept of FM is essential to a wide gamut of radio frequency wireless devices and is therefore worth studying in 2007. [1] The objective of this project is to explain the design and construction of a simple FM transmitter. The salient specifications for the transmitter are as follows: one 3Volt supply, DC power consumption less than 80mW, transmit frequency at a vacant spot in FM band (88MHz-108MHz), transmitted power not to exceed 10uW, and the only active device type allowed is the BC547 NPN BJT. In addition, a pre-emphasis filter is required with a 3dB corner frequency equal to 1 / 75us. A variable capacitor with value 4pF .30pF is used for tuning. The design has been simulated and constructed. The built transmitter can transmit music at a distance of 300 meters. This project will explain the design decisions that were made in the process of design and construction. It is surprisingly powerful despite its small component count and 3Volt operating voltage. It will easily penetrate over three floors of an apartment building and go over 300 meters in the open air.

FM TRNSMITTER CIRCUIT DESCRIPTION

The circuit is basically a radio frequency (RF) oscillator that operates around 100 MHz audio picked up and amplified by the electrets microphone is fed into the audio amplifier stage built around the first transistor. Output from the collector is fed into the base of the second transistor where it modulates the resonant frequency of the tank circuit (the 5 turn coil and the trim cap) by varying the junction capacitance of the transistor. Junction capacitance is the function of the potential...
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