What is Radio?

Radio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light.

Definitions

•      Frequency

Radio frequency (RF) is the rate of oscillation in the range of about 30 kHz to 300 GHz, which corresponds to the frequency of electrical signals normally used to produce and detect radio waves

•       Modulation

Adding information to a carrier signal is a process called modulation. To modulate a radio carrier means that it is changed in some way to correspond to the speech, music, or data it is to carry

•       Electromagnetic Waves

Radio signals exist as a form of electromagnetic wave. These radio signals are the same form of radiation as light, ultra-violet, infra-red, etc., differing only in the wavelength or frequency of the radiation. Electromagnetic waves have two elements. They are made from electric and magnetic components that are inseparable

Medium of Mass Communication

•     Easily accessible and affordable.

•     Oral medium of Communication.

•     low production cost and extreme versatility.

•     Capacity to provoke dialogue.

•     Participation of local population is possible.

•     Information dissemination is simple.

•     A tool for democratization.

•      A platform for expression of ideas .

•      An agent for social change.

•      Tool for exchange of knowledge and   technologies.

•      Tool for cultural expression and entertainment.

Characteristics of Radio

•     Audio medium of communication

•      Portable

•      Affordable

•     Greatest reach

•      Easy educational medium

            Example:  In rural areas-high illiteracy rate…

•     Alternative media to the imperfections of public and commercial media

Types of Radio Stations

•     National Radio serving the whole of the country

•     Regional Stations covering areas or a group of city areas

•     Local Radio, smaller local area transmission (similar say to a local newspaper area coverage.)

•     Community Radio, not for profit radio station broadcasting to particular defined communities

•     RSL, short term time restricted service licences

•     DAB stations transmitting only via a digital network

•     Internet, satellite and cable stations

•     Hospital, Student or campus radio

•     Pirate radio, illegal and unlicensed broadcasting

Modes of Transmission

•     Amplitude Modulation

•     Frequency Modulation

•     Short Wave

•     Medium Wave

•     Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave.

•     AM works by varying the strength of the transmitted signal in relation to the information being sent.

•     The frequency remains constant.

•     Frequency Modulation

•     It conveys information over a carrier wave by varying its instantaneous frequency.

•     Was invented by Edwin Howard Armstrong.

•     It requires a wider signal bandwidth than AM.

•     Signal robust against Noise.

•     High frequency and fidelity radio transmission is achieved.

Short Wave

•     It refers to the high frequency portion of the radio spectrum

•     The frequency ranges between 3,000–30,000 kHz (3–30MHz).

•     Shortwave radio received its name because its frequencies were higher (and wavelengths shorter) than the medium and low frequency bands then used for radio communications.

Advantages of Short wave

•     Government authorities have technical difficulties to monitor which stations are being listened to unlike Internet.

Eg: During the coup against President Mikhail Gorbachev, when his access to communications was limited, Gorbachev was able to stay informed by means of the BBC World Service on shortwave.

•     Low-cost shortwave radios are widely available in all but the most repressive countries in the world.

•     Many newer shortwave receivers are portable and can be battery operated, making them useful in difficult circumstances.

•     Shortwave radios can be used in situations where Internet or satellite technology is unavailable (or unaffordable).

•     Shortwave radio travels much farther than broadcast FM.

•     Shortwave broadcasts can be easily transmitted over a distance of several thousands of kilometers

      Eg: from one continent to another, especially at night particularly in tropical regions.

•     SW is somewhat less prone to interference from thunderstorms than Mediumwave and is able to cover a large geographic area with relatively low power

Disadvantages of Short wave

•     Shortwave broadcasts often suffer from serious interference problems because of overcrowding on the wavebands, atmospheric disturbances and electrical interference problems (particularly in cities) from TV sets, computers, poorly designed domestic appliances, and substandard electrical installations.

•     Even under ideal reception conditions, the audio quality of a shortwave broadcast is usually inferior to that of domestic stations, particularly FM stations, and it is always in mono.

Medium Wave

•     It is that part of the medium frequency (MF) radio band used mainly for AM broadcasting.

•     Medium wave signals have the property of following the curvature of the earth (the ground wave) at all times, and also refracting off the ionosphere at night (sky wave).

This makes this frequency band ideal for both local and continent-wide service, depending on the time of day.