The Design and Construction of FM Radio Transmitter
Chapter One
OBJECTIVE OF THE STUDY
The objective of this project is:
- To review some modern digital technologies that have been developed for effective FM signal generation.
- To show the design and components of an FM transmitter
- To show the construction process of an electronically operated system known as an FM transmitter capable of transmitting a frequency-modulated signal.
CHAPTER TWO
LITERATURE REVIEW
FM THEORY
Angle and amplitude modulation are techniques used in communication to transmit data or voice over a particular medium, whether it be over wire cable, fibre optic or air (the atmosphere). A wave that is proportional to the original baseband (a real time property, such as amplitude) information is sued to vary the angle or amplitude of a higher frequency wave (the carrier)
Carrier = A Cos φ(t)
Φ(t) = 2πfc t + α
Where A is the amplitude of the carrier and Φ(t) is the angle of the carrier, which constitutes the frequency (fc) and the phase (α) of the carrier. Angle modulation varies the angle of the carrier by an amount proportional to the information signal. Angle modulation can be broken into 2 distinct categories, frequency modulation and phase modulation (Mohn, 2007).
PHASE MODULATION (PM)
Angle modulation in which the phase of a carrier is caused to depart from its reference value by an amount proportional to the modulating signal amplitude.
FREQUENCY MODULATION (FM)
Angle modulation in which the instantaneous frequency of a sine wave carrier is caused to depart from the carrier frequency by an amount proportional to the instantaneous value of the modulator or intelligence wave (Kelly, 2010).
Phase modulation differs from Frequency modulation in one important way. Take a carrier of the form A Cos (ωct + θ) = Re {A.ej(ωct + θ)}
PM will have the carrier phasor in between the + and – excursions of the modulating signal. FM modulation also has the carrier in the middle but the fact that when you integrate the modulating signal and put it through a phase modulator you get FM, and if the modulating wave were put through a differentiator before a frequency modulator you get a phase modulated wave. This may seem confusing at this point, but the above concept will be reinforced further in the sections to follow.
METHOD OF FREQUENCY MODULATION
Angle modulation is the proper term for modulation by changing the instantaneous frequency or phase of the carrier signal. True FM and phase modulation are the most commonly employed forms of analogue angle 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 (Correy, 2012).
CHAPTER THREE
CONSTRUCTION
HARDWARE CONSTRUCTION AND IMPLEMENTATION
Some of the items used for the construction were bought from different manufacturers. For instance the transmitter casing, the 9volt battery and the condenser microphone were bought alongside other materials. The construction followed several steps.
STEP 1:
The process starts by choosing the positive line in the vero board and connecting the positive terminal of the microphone in series with the2.2kresistor and connect the other sodto the positive line in the vero board.
CHAPTER FOUR
ANALYSIS AND DISCUSSION OF RESULTS
TESTING
To test the workability of the constructed transmitter, the following procedures were followed:
CHAPTER FIVE
SUMMARY AND CONCLUSION
PROBLEMS ENCOUNTERED
One of the problems encountered was getting the necessary components to complete this project work here in Abraka, Delta State, we went as far as Warri, Obiaruku, Agbor and even Benin to get some of the components also one of the issues presented was that the drill was broken repeatedly, phenolic plate had to get back to you in error and was removed bad pulse copper.
For the coil only had to squeeze more hoops to send the same signal but without much noise. As for the trimmer, did not know that it changes the impedance of the metal, so it was necessary to align with a plastic screwdriver. These are the main problems we encountered.
RECOMMENDATION
The process in which this project took me through has made me see some areas in which the design can be upgraded and further study carried out to improve the quality of the FM transmitter and these areas include:
I recommend that a FM Transmitter with LCD that will show the frequency in the transmitter operates on should be researched into.
CONCLUSION
Block-by-block design and construction of the FM transmitter and receiver was the right approach. I became familiar with the benefits and limitations of each stage and could optimize them individually in the first few weeks. When integration occurred, the firsthand knowledge of the separate blocks became an invaluable part of debugging.
The goal of this project was to create an FM transmitter, which transmits, it redundancy, a signal or sound to an FM receiver, without the need for cables.This goal was achieved and the signal produced can be heard on stations already occupied with a frequency, i.e. to listen to our sound emitted at the transmitter, we search the FM band station or frequency that is free or empty.
REFERENCES
- “FM broadcasting in the United States” http://en.wikipedia.org/wiki/FM broadcasting in the USA
- “Phase-Locked Loop Tutorial, PLL” http://www.sentex.ca/~mec199/gadgets/pll/pll.html “The Future of Radio”. The Swedish Radio and TV Authority, 2008
- Ackermann, J. (2013). “TARR: Tomorrow’s Ham Radio Technology Today”.
- Correy, D. (2011). “HD Radio: What it is and What it is not”, http://abot.com/od/hdradio/a/aa092706a.htm
- David Chen (2002) Design and Construction of FM Transmitter and Receiver – Final Report http://ww1dc53e8f_2.pdf
- Durant., L. (2006) “HD Radio: A Viable Alternative to Satellite?” October, 2006
- Ferrara D. (2014). “Advantages and Disadvantages of HD Radio” USA.
- Groome B. (2014). HD Radio (I.B.O.C.)”. http://circuit-zone.com/?cat=fm_transmitters
- http://www.electronics-diy.com/intro_txfm.php
- Carr Joseph, J.(1997). Microwave and Wireless Communication Technology, Newnes, 1997 ISBN 0750697075 page 339-341
- Kelly C.W. (2010). “HD – Radio: Real World Results in Asia”, USA.
- Kelly, C.W. (2010). Digital HD Radio AM/FM Implementation Issues”, USA.
