21-03-2014, 01:02 PM
Institutional Radio Broadcasting
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Abstract
Community radio (CR) is a participatory medium and a subset of Radio broadcasting. It is an inexpensive and popular way for disseminating content such as information, news, entertainment, etc. Community Radio is designed to increase availability of localized information, media access and empowerment, societal resource distribution for the community, and even for the educational purpose. Frequency modulation has several advantages over the system of amplitude modulation used in the alternate form of radio broadcasting. The most important of these advantages is that an FM system has greater freedom from interference, various electrical disturbances, such as those caused by thunderstorms and car ignition systems create amplitude modulated radio signals that are received as noise by AM receivers. A well-designed FM receiver is not sensitive to such disturbances when it is tuned to an FM signal of sufficient strength. The signal-to-noise ratio in an FM system is much higher than that of an AM system. FM broadcasting stations 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 with wavelengths between 3.4 and 2.77 meters respectively and will be the intended frequency range of transmission The aim of the work is to develop a Miniaturized low power FM Transmitter to be used as a community radio.
Introduction
The constant technological developments in radio since the discovery of the first experiments by Guglielmo Marconi, plus the contributions of the inventions of James Maxwell and Heinrich Hertz, made the radio became a vehicle of mass communication. Comparatively low cost of equipment for an FM broadcasting station resulted in rapid growth in the years following World War II. Because of crowding in the AM broadcast band and the inability of standard AM receivers to eliminate noise the tonal fidelity of standard stations is purposely limited. FM does not have these drawbacks and can be used to transmit information content, reproducing the original performance with a degree of fidelity that cannot be reached on AM bands. The integrated chip has also played its part in the wide proliferation of FM receivers, as circuits got smaller it became easier to make a modular electronic device which enables the portability of a tape player and an AM/FM radio receiver. This has resulted in the portability of a miniature FM receiver.
concept of community radio
Community Radio is a non-profit service that is owned and managed by a particular community usually through a trust, foundation, or association. Its aim is to serve and benefit that community.
[b] Aim and Concept[/b]
Community Radio (CR) aims at providing service to a particular community, institution or for a group of people. CR’s small scale and local broadcast allows content to be more localized than from commercial or national radio stations.
Our aim is to set up an Institutional Radio which can cover a region of less than one km. This is to cover the entire region of our institution, which can be used exclusively for educational as well as for other special purpose. Output radiated power of about 1 watt can be used to transmit the signal over the specified region. Omni directional antennas are to be used to establish transmission of signals over the entire region.
Advantage of FM Over AM
Frequency modulation has several advantages over the system of amplitude modulation (AM) used in the alternate form of radio broadcasting. The most important of these advantages is that an FM system has greater freedom from interference, various electrical disturbances, such as those caused by thunderstorms and car ignition systems create amplitude modulated radio signals that are received as noise by AM receivers. A well-designed FM receiver is not sensitive to such disturbances when it is tuned to an FM signal of sufficient strength. The signal-to-noise ratio in an FM system is much higher than that of an AM system. FM broadcasting stations can be operated in the very-high-frequency bands at which AM interference is frequently severe. Frequency modulated wave is less susceptible to interferences from buildings, traffic etc which provides improved signal to noise ratio.
Thus for setting up of Institutional Radio, Frequency Modulation is to be used which is more efficient than the Amplitude Modulation.
Low Power FM Transmitter
The Institutional Radio which uses FM modulation consists of different stages like Oscillator, Pre-Amplifier, Driver and the Power Amplifier. It can transmit signal in the frequency range of 88-108 MHz, which depends on the frequency generated by the oscillator stage. Output Power of about 1 watt is required to obtain a range of about 750 meter, which is enough to cover the entire Institution. Omni directional antenna is to be used so that the signal can be transmitted over the entire 360°, so that by placing transmitter at the centre, the entire region can be covered.
Conclusion
Institutional Radio which can be used to broadcast signals, mainly for educational purpose can be accomplished by using this four stage FM transmitter. For continuous operation of the transmitter within the Institution proper sanction from the government is required. Frequency Modulation of the information signal is done because of its inherent advantages as mentioned above. The range of the transmitter can be increased by using high power transmitters or by using more number of amplifying stages. Proper matching between the load antenna and the output stage must be made for the improvement of output power transmitted.