CHARACTERISTICS OF RADIO
11.0 Objective of the lesson :
The objective of this lesson is to assist you in
- Understanding the concept of radio
- Understanding the characteristics of radio
- Learning the advantages and disadvantages of traditional radio
- Learning the advantages of internet/satellite radio
- Learning the advantages of Community radio
Structure of the lesson :
- Introduction to radio
- Advantages of radio
- Advantages of Sattelite radio
- Advantages of Community radio
- Disadvantages of radio
- Summary
- Technical Terms
- Model Questions
- Refernce Books
Radio is the wireless transmission of signals, by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. It does not require a medium of transport. Information is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude or their frequency. When radio waves pass an electrical conductor, the oscillating fields induce an alternating current in the conductor. This can be detected and transformed into sound or other signals that carry information.
The word ‘radio’ is used to describe this phenomenon, and radio transmissions are classed as radio frequency emissions.
Uses of radio
Early uses were maritime, for sending telegraphic messages using Morse code between ships and land. The earliest users included the Japanese Navy scouting the Russian fleet during the Battle of Tsushima in 1905. One of the most memorable uses of marine telegraphy was during the sinking of the RMS Titanic in 1912, including communications between operators on the sinking ship and nearby vessels, and commu- nications to shore stations listing the survivors. The first radio couldnt transmitt sound or speech and was called the “wireless telegraph”
Radio was used to pass on orders and communications between armies and navies on both sides in World War I; Germany used radio communications for diplomatic messages once its submarine cables were cut by the British, The United States passed on President Woodrow Wilson’s Fourteen Points to Germany via radio during the war. Broadcasting began from San Jose in 1909, and became feasible in the 1920s, with the widespread introduction of radio receivers, particularly in Europe and the United States.
Besides broadcasting, point-to-point broadcasting, including telephone messages and relays of radio programs, became widespread in the 1920s and 1930s. Another use of radio in the pre-war years was the development of detecting and locating aircraft and ships by the use of rader (Radio Detection And Rang- ing).
Today, radio takes many forms, including wireless networks and mobile communications of all types, as well as radio broadcasting. Before the advent of television, commercial radio broadcasts included not only news and music, but drams, comedies, variety shows, and many other forms of entertainment. Radio was unique among methods of dramatic presentation in that it used only sound. For more, see radio program- ming.
Audio
A Fisher 500 AM/FM hi-fi receiver from (1959. AM broadcast radio sends music and voice in the Medium Frequency (MF-0.300 MHz) radio spectrum. AM radio uses amplitude modulation, in which the amplitude of the transmitted signal is made proportional to the sound amplitude captured (transduced) by the micro- phone while the transmitted frequency remains unchanged. Transmissions are affected by static and interference because lightning and other sources of radio that are transmitting at the same frequency add their amplitude to the original transmitted amplitude. The most wattage an AM radio station is allowed to use is 50,000 watts and the only stations that can blast out signals this powerful were grandfathered in; these include WJR and CKLW.
FM broadcast radio sends music and voice with higher fidelity than AM radio. In frequency modulation, amplitude variation at the microphone causes the transmitter frequency to fluctuate. Because the audio signal modulates the frequency and not the amplitude, an FM signal is not subject to static and interfer- ence in the same way as AM signals. FM is transmitted in the Very High Frequency (VHF-30 MHz to 300 MHz) radio spectrum. VHF radio waves act more like light, travelling in straight lines, hence the reception range is generally limited to about 50-100 miles. During unusual upper atmospheric conditions, FM signals are occasionally reflected back towards the Earth by the ionosphere, resulting in Long distances FM reception, FM receivers are subject to the capture effect, which causes the radio to only receive the strongest signal when multiple signals appear on the same frequency. FM receivers are relatively immune to lightning and spark interference.
FM Sub-carrier services are secondary signals transmitted “piggyback” along with the main program, Special receivers are required to utilize these services. Analog channels may contain alternative program- ming, such as reading services for the blind, background music or stereo sound signals. In some ex- tremely crowded metropolitan areas, the sub-channel program might be an alternate froeign language radio program for various ethnic groups. Sub-carriers can also transmit digital data, such as station identification, the current song’s name, web addresses, or stock quotes. In some countries, FM radio automatically re-tune themselves to the same channel in a different district by using sub-bands.
Aviation voice radios use VHF AM. AM is used so that multiple stations on the same channel can be received (Use of FM would result in stronger stations blocking out reception of weaker stations due to FM’s capture effect). Aircraft fly high enough that their transmitters can be received hundred of miles (or kilometres) away. even though they are using VHF.
Marine voice radios can use AM in the shortwave High Frequency (HF-3 MHz to 30 MHz) radio spectrum for very long ranges or marrowband FM in the VHF spectrum for much shorter ranges. Government, police, fire and commercial voice services use narrowband FM on special frequencies. Fidelity is sacrificed to use a smaller range of radio frequencies, usually five KHz of deviation, rather than the 75 KHz used by FM broadcasts and 25 KHz used by TV sound.
Civil and military HF (high frequency) voice services use shortwave radio to contact ships at sea, aircraft and isolated settlements. Most use single sideband voice (SSB), which uses less band width than AM. On an AM radio SSB sounds like ducks quacking. Viewed as a graph of frequency versus power, an AM signal shows power where the frequencies of the voice add and subtract with the main radio frequency. SSB cuts the bandwidth in half by suppressing the carrier and (usually) lower sideband. This also makes the trans- mitter about three times more powerful, because it doesn’t need to transmit the unused carrier and sideband.
TETRA, Terrestrial Trunked Radio is a digital cell phone system for military, police and ambulances, Commercial services such as XM, WorldSpace and Sirius offer encrypted digital Satellite radio.
Telephony
Mobile phones transmit to a local cell site (transmitter/receiver) that ultimately connects to the public switched telephone network (PSTN) through an optic fiber or microwave radio and other network ele- ments. When the mobile phone nears the edge of the cell site’s radio coverage area, the central computer switches the phone to a new cell. Cell phones originally used FM, but now most use various digital modu- lation schemes. Satellite phones use satellites rather than cell towers to communicate. They come in two types: INMARSAT and Iridium. Both types provide world-wide coverage. INMARSAT uses geosynchronous satellites, with aimed high-gain antennas on the vehicles. Iridium uses 66 Low Earth Orbit satellites as the cells.
Video
Television sends the picture as AM and the sound as FM, with the sound carrier a fixed frequency (4.5 MHz in the NTSC system) away from the video carrier. Analog television also uses a vestigial sideband on the video carrier to reduce the bandwidth required.
Digital television uses 8VSB modulation in North America (under the ATSC digital television standard), and COFDM modulation elsewhere in the world (using the DVB-T standard). A Reed-Solomon error correction code adds redundant correction codes and allows reliable reception during moderate data loss. Although many current and future codecs can be sent in the MPEG-2 transport stream container format, as of 2006 most systems use a standard-definition format almost identical to DVD: MPEG-2 video in Anamorphic widescreen and MPEG layer 2 (MP2) audio. High-definition television is possible simply by using a higher resolution picture, but H.264/AVC is being considered as a replacement video codec in some regions for its improved compression. With the compression and improved modulation involved, a single “channel” can contain a high-definition program and several standard-definition programs.
Navigation
All satellite navigation systems use satellites with precision clocks. The satellite its position, and the time of the transmission. The receiver listens to four satellites, and can figure its position as being on a line that is tangent to a spherical shell around each satellite, determined by the time-of-flight of the radio signals from the satellite. A computer in the receiver does the maths.
Radio direction-finding is the oldest form of radio navigation. Before 1960 navigators used movable loop antennas to locate commercial AM stations near cities. In some cases they used marine radiolocation beacons, which share a range of frequencies just above AM radio with amateur radio operators. Loran systems also used time-of-flight radio signals, but from radio stations on the ground. VOR (Very High Frequency Omnidirectional Range), systems (used by aircraft), have an antenna array that transmits two signals simultaneously. A directional signal rotates like a lighthouse at a fixed rate. When the directional signal is facing north, an omnidirectional signal pulses. By measuring the difference in phase of these two signals, an aircraft can determine its bearing or radial from the station, thus establishing a line of position. An aircraft can get readings from two VORs and locate its position at the intersection of the two radials, known as a “fix.” When the VOR station is callocated with DME (Distance Measuring Equipment), the aircraft can determine its bearing and range from the station, thus providing a fix from only one ground station. Such stations are called VOR/DMEs. The military operates a similar system of navaids, called TACANs, which are often built into VOR stations. Such stations are called VORTACs. Because TACANs include distance measuring equipment, VOR/DME and VORTAC stations are identical in navigation potential to civil aircraft.
Radar
Radar (Radio Detection And Ranging) detects objects at a distance by bouncing radio waves off them. The delay caused by the echo measures the distance. The direction of the beam determines the direction of the reflection. The polarization and frequency of the return can sense the type of surface. Navigational radars scan a wide area two to four times per minute. They use very short waves that reflect from earth and stone. They are common on commercial ships and long-distance commercial aircraft.
General purpose raders generally use navigational radar frequencies, but modulate and polarize the pulse so the receiver can determine the type of surface of the reflector. The best general-purpose radars distin-
guish the rain of heavy storms, as well as land and vehicles. Some can superimpose sonar data and map data from GPS position.
Search radars scan a wide area with pulses of short radio waves. They usually scan the area two to four times a minute. Sometimes search radars use the doppler effect to separate moving vehicles from clutter. Targeting radars use the same principle as search radar but scan a much smaller area far more often, usually several times a second or more. Weather radars resembe search radars, but use radio waves with circular polarization and a wavelength to reflect from water droplets. Some weather radar use the doppler to measure wind speeds.
Emergency services
Emergency Position-Indicating Radio Beacons (EPIRBs), Emergency Locating Transmitters (ELTs) or Personal Locator Beacons (PLBs) are small radio transmitters that satellites can use to locate a person or vehicle needing resue. Their purpose is to help rescur people in the first day, when survival is most likely. There are several types, with widely-varying performance.
Data (digital radio)
Most new radio systems are digital, see also: Digital TV, Satellite Radio, Digital Audio Broadcasting. The oldest form of digital broadcast was spark gap telegraphy, used by pioneers such as Marconi. By pressing the key, the operator could send messages in Morse code by energizing a rotating commutating spark gap. The rotating commutator produced a tone in the receiver, where a simple spark gap would produce a hiss, indistinguishable from static. Spark gap transmitters are now illegal, because their transmissions span several hundred megahertz. This is very wasteful of both radio frequencies and power.
The next advance was continuous wave telegraphy, or CW (Continuous Wave), in which a pure radio frequency, produced by a vacuum tube electronic oscillator was switched on and off by a key. A receive with a local oscillator would “heterodyne” with the pure radio frequency, creating a whistle-like audio tone. CW uses less than 100 Hz of bandwith. CW is still used, these days primarily by amateur radio operators (hams), Strictly, on-off keying of a carrier should be known as “Interrupted Continuous Wave” or ICW or on-off keying (OOK).
Radio teletypes usually operate on short-wave (HF) and are much loved by the military because they create written information without a skilled operator. They send a bit as one of two tones. Groups of five or seven bits become a character printed by a teletype. From about 1925 to 1975, radio teletype was how most commercial messages were sent to less developed countries. These are still used by the military and weather services.
Aircraft use a 1200 Baud radioteletype service over VHF to send their ID, altitude and position, and get gate and connecting-flight data. Microwave dishes on satellites, telephone exchanges and TV stations usually use quadrature amplitude modulation (QAM). QAM sends data by changing both the phase and the amplitude of the radio signal. Engineers like QAM because it packs the most bits into a radio signal when given an exclusive (non-shared) fixed narrowband frequency range. Usually the bits are sent in “frames” that repeat. A special bit pattern is used to locate the beginning of a frame.
Communication systems that limit themselves to a fixed narrow band frequency range are vulnerable to jamming. A variety of jamming-resistant spread spectrum techniques were initially developed for military use, most famously for Global Positioning System satellite transmissions. Commercial use of spread spectrum begin in the 1980s. Bluetooth, most cell phones, and the 802. 11b version of Wi-Fi each use various forms of spread spectrum.
Systems that need reliability, or that share their frequency with other services, may use “coded orthogonal frequency-division multiplexing” or COFDM breaks a digital signal into as many as several hundred slower subchannels. The digital signal is often sent as QAM on the subchannels. Modern COFDM systems use a small computer to make and decode the signal with digital signal processing, which is more flexible and far less expensive than older systems that implemented separate electronic channels. COFDM resists fading and ghosting because the narrow-channel. QAM signals can be sent slowly. An adaptive system, or one that sends error-correction codes can also resist interference, because most interference can affect only a few of the QAM channels. COFDM is used for WiFi, some cell phones, Digital Radio Mondiale, Eureka 147, and many other local area network, digital TV and radio standards.
Heating
Radio-frequency energy generated for heating of objects is generally not intended to radiate outside of the generating equipment, to prevent interference with other radio signals. Microwave ovens use intense radio waves to heat food. (Note: It is a common misconception that the radio waves are tuned to the resonant frequency of water molecules. The microwave frequencies used are actually about a factor of ten below the resonant frequency.) Diathermy equipment is used in surgery for sealing of blood vessels. Induction furnaces are used for melting metal for casing.
Mechanical force
Tractor beams can use radio waves which exert small electrostatic and magnetic forces. These are enough to performs station-keeping in microgravity environments. Conceptually, spacecraft propulsion: Radiation pressure from intense radio waves has been proposed as a propulsion method for an interstellar probe called Starwisp. Since the waves are along, the probe could be a very light metal mesh, and thus achieve higher accelerations than if it were a solar sail.
Amateur Radio service
Amateur radio is a hobby in which enthusiasts purchase or build their own equipment and use radio for their own enjoyment. They may also provide an emergency and public-service radio service. This has been of great use, saving lives in many instances. Radio amateurs are licensed to use frequencies in a large number of narrow bands throughout the radio spectrum. They used all forms of encoding, including obsolete and experimental ones. Several forms of radio were pioneered by radio amateurs and later became commercially important including FM, single-sideband (SSB), AM, digital packet radio and satellite repeaters. Some amateur frequencies may be disrupted by power-line internet service.
Unlicensed radio services
Personal radio services such as Citizens’ Band Radio, Family Radio Servce, Multi-Use Radio Service and others exist in North America to provide simple, (usually) short range communication for individuals and small groups, without the overhead of licensing. Similar services exist in other parts in other parts of the world. These radio services involve the use of handheld units.
Radio control (RC)
Radio remote control use of radio waves to transmit control data to a remote object as in some early forms of guided missile, some early TV remotes and a range of model boats, cars and airplanes. Large industrial remote-controlled equipment such as cranes and switching locomotives now usually use digital radio techniquies to ensure safety and reliability.
In Madison Square Garden, at the Electrical Exhibiton of 1898, Nikola Tesla successfully demonstrated a radio-controlled boat. He was awarded U.S. patent No. 613,809 for a “Method of and Apparatus for Controlling Mechanism of Moving Vessels or Vehicles.”
In the marketing world, radio has earned the reputation of being the odd step-cousin.
Much of that reputation comes from radio being tough to track. On one hand, radio does work. Businesses do notice an increase in sales when they add radio to the mix. However, radio doesn’t test well. In surveys and other tracking methods, radio tends to be the one with the dismal scores.
Radio works on a subconscious or unconscious level. People remember the ad, but not that they heard it on the radio. So, they tend do credit a different medium for the ad, like the yellow pages. Yellow pages gets a boost while radio drops a few points.
Regardless, radio should not be ignored because it does work. and many marketing consultants will probably tell you radio is an excellent medium to reach a local market. The new technology has also given a boost to radio.
Internet radio shows are starting to take off in a big way. That means advertising and sponsorship opportu- nities are also taking off. In addition, “offline” methods have been shown to be pretty effective at driving traffic online.
Depending on the costs of radio in a community, radio may be a very affordable way to get a good viral campaign going. (A viral campaign is when your customers send promotional items about your business such as e-mails, articles, Web site urls, etc. to their friends and family members.)
Affordable
When you compare spot to spot, radio tends to be one of the least expensive media out there. However, one spot is not going to do it. To reach your target market, you need to purchase several spots. That’s why radio can also turn into one of the more expensive media. However, there are ways to keep your costs in line yet still reap customers are more likely to hear your message.
Psychological, if you voice the commercials yourself
Hearing your voice makes people feel like they “know” you. (Hence the popularity to audio on Web sites. In fact, marketing gurus claim just by adding audio to a site substantially increases how many people buy.)
People tend to buy from people and businesses they know and trust. Hearing your voice helps them feel as if they know you. These psychological aspects may be another reason to consider running a few radio ads in your local market even if you have an Internet business.
Speed You can get your spot up and running in no time.
Loyalty
Listeners choose stations based on the music or shows they like and they tend to be quite loyal to that station. If you know what your customers enjoy listening to, it’s an excellent way to reach them.
Good support medium
Radio works really well when paired with other marketing mediums (like print, direct mail or television). But for every positive, there’s a negative. In the spirit of being objective, here are a few for radio.
Background medium
Radio tends to be on in the background, which means it tends to be ignored. Generally, your target market needs to be exposed to your ad more times than other marketing media before they’ll act upon your message.
Little staying power
The lack of visuals again keeps radio from “sticking” with people. At least, that’s what some of the market- ing gurus say. And if you can write a spot that create pictures in your customers heads, you can actually work this to your advantage.
IN A NUTSHELL
Advantages of Radio
- Segmented
- Lead time
- Affordable
- Mental imagery
- Commuter audience
- Frequency and IMC
- Loyalty
One of the great advantages of satellite radio is the fact that the programs are not interrupted by commer- cials. This is because the provider’s income comes from listerners and not from advertisers. Satellite radio services offer around 70 programs of commercial fee music channels each and you have a great variety of choices, from maintream rock, hip-hop and dance music of folk music, opera, blues and many more.
Another great thing about satellite radio is the absence of static. Even if a person is driving from one end of the country to another, he will not get any static at all on the way. The satellite radio signal is digital, which means that receivers will get crystal-clear sound wherever you go.
Satellite radio tuners receive, along with the actual radio programs, an influx of metadata that consists of information regarding song title, artist, radio program and radio channel. This means that the user’s satellite radio receiver will display all the necessary information about what he/she is listening to. For instance, if a person hears a great song and he wants to know which artist sings it, he can just look at the receivers’s display.
All satellite radio programs are uncensored. Listeners can also listen to your favorite hip-hop songs without the interruption of those annoying ‘beep’ sounds.
Satellite radio programs also offer information about local traffic and weather conditions. The information is very detailed especially for those who live in big cities. If there is a major national calamity and other terrestrial radio stations will not work, a person can always cound on getting accurate information from satellite radio program. He can also listen to satellite radio online on his computer.
Traditional radio iis not free, despite the popular belief. It is time-consuming and irritating because a person has to listen to five minutes or more of commercials so that he can finally hear a song you like. The satellite radio subscriptions are very affordable and, for very low price a person can get exactly the pro- grams he wants, which he can listen to wherever he is, at the best sound quality.
Satellite radio is wonderful especially for people who travel a lot. If a person is travelling across the coun- try, for example, he can listen to the channel or channel he wants during his whole trip, without losing signal or getting static. If he has a traditional radio, he will have to keep changing channels every hundred miles, but if he is using satellite radio he does not have to do that because the geographically availability to programs is not a problem. Satellite radio subscribers will soon get the chance to watch video programs as well. Both Sirius and XM services have announced their intention of introducing in the near future a variety of video satellite channels that will have some of the great advantages that are currently available to satellite radio: commercial free programs, great quality of sound and vast geographical availability.
Community radio is a type of radio service that caters to the interests of a certain areas, broadcasting material that is popular to a local audience but is overlooked by more powerful broadcast groups. The term has somewhat different meanings in the United Kingdom, the United States, Canada, and Austrialia. In the UK, the idea for originating community radio came in part from the situation of many illegal pirate radio stations having been established by the influx of Afro-Caribbean immigrants in cities such as London, Birmingham, Bristol, and Manchester in the 1970s. Therefore, “community radio” remains synonymous with “pirate radio” for many people there, but despite the intentions being similar, the results are vastly different. In America, community radio is more commonly non-profit and non-commercial, often using licensed class DFM band transmitters, although pirate radio outlets have been operated in many places.
Canadian and Australian community stations operate somewhat similarly to their American counterparts.
With the advent of community broadcasting, a whole new exciting world awaits listeners in far-flung areas where radio listening revolves around community centres. The proposed community radio serves to bring small groups together through their own participation to reflect their day-to-day concerns. The community will participate by creating contents of the programmes for its own people. This narrow broad casting does not require big transmitters.
Community radio of the future will strive to bring people together through interactions. Like teleconferenc- ing, the listeners will be able to talk to each other through the radio network using small wireless sets. This will help in business activities of the particular district or a village where the artisan will know his prospec- tive buyer for his wares.
At present, however, programmes will be created for the listeners in the community and reflect what is relevant for their needs and aspirations.
The community in these areas is well-knit. There is always collective response to all radio programmes as the listeners generally assemble at one place where they listen to radio programmes, discuss and react. This turns into public service broadcast because it is here that the aspirations of the people can be ful- filled. To achieve this, the programmes have to be drawn up with a foresight keeping in mind the priorities of varied areas so that people can easily identify themselves with the programmes.
Out of the existing network of All India Radio, the Frequency Modulation, commonly known as the FM, technique of the radio wave has a distinct advantage. The Medium Wave and Short Wave suffer from the disadvantage of deteriorating sound quality with the increase in distance. The FM provides stereo quality and is ideal for short-range broadcasts. In the far-flung rural areas where the availability of power supply is unreliable, the FM is ideally suited for community broadcasts for dissemination of information, education and entertainment. The Working Group on the 10th Plan has recommended future expansion of radio, primarily in the FM mode.
To supplement the broadcasting by All India Radio, the Government, in July 1999, approved private Participation in FM broadcasting.
After offering licences to private FM broadcasting in 40 cities through 110 channels for commercial broad- casting, the Government has decided to offer private licences to the established educational institutions and organizations having their own campus and residential schools.
At present, AIR has 133 FM transmitters covering more than 21 percent of area and about 31 percent population of the country. Private licences for FM broadcasting have been offered in 40 cities for 110 channels for setting up 10 KW radio transmitters, except in four metro cities where the capacity could be between 10 to 20 KW. These private channels are already operating in Delhi, Mumbai, Kolkata, Chennai, Bangalore, Indore, Ahemedabad, Pune and Lucknow. Next in the line are Patna, Bhuvaneswar, Cuttack, Jabalpur, Coimbatore, Tirunelveli and Vishakhapatnam. The number of channels will provide plurality of choice to the listeners leading to improvement in the quality of programmes.
To start with, programmes on the comunity radio service will focus on issues relating to education, health, environment, agriculture and rural and community development. The Governement expects these programmes to be popular if done innovatively done to sustain the listener’s interest.
This service is expected to provide a platform for students and teachers to give expression to their creative talent in producing programmes and in socio-cultural cohesion of the masses at the local level. The licencees will not be allowed to broadcast any news, current affairs programmes, election and political broadcasts. They will also not be allowed to air any advertisement of sponsored programmes.
The Government is aware of the need to safeguard the radio stations from being misused for undesirable propaganda against national interest and safety and security of the countr. Therefore, in the first phase, the Government has given licenses to only the selected and established educational institutions in the country for community broadcasts.
For the sake of credibilitey, the licenses will ensure that nothing is included in the programme that goes against good taste and decency. The code of conduct rules out anything obscene, defamatory and innuen- dos. The licencees will also ensure that there is nothing that amounts to contempt of court or by casting aspersions on the integrity of the President or the Judiciary.
The programme code will almost be the same as for All India Radio. It would strive to promote national integration, religious harmony, scientific temper and Indian culture.
The applicant will be permitted only one licence valid for three years and the licencee will provide service on free-to-air basis. No channel will be permitted for commercial purposes. The Government will have the right to inspect broadcast facilities and reserve the right to take over the entire services or network or revoke or suspend the licence in the interest of national security.
The licensee will ensure that all foreign personnel likely to be appointed as employees or consultants obtain security clearance from the Government.
The licensee will be expected to furnish a bank guarantee to ensure timely performance of the licensee agreement and failure to start the services within the stipulated period can result in cancellation of licence and forfeiture of the bank guarantee.
The people are likely to immensely benefit from community radio because of its inter-active nature and low costs of broadcasting. (PIB Features)
Radio is only an ‘ear’ medium. The absence of audio-visual input makes visualisation of a scene or a product or a person difficult. For e.g., in the case of radio advertising, listeners may find it difficult to visualise the image for a product that needs to be identified visually in a retail store. In case of listening to an interview of a scientist, the listeners cannot see him and thus will never know what he looks like.
Thus the main disadvantages of radio include: audio only; fleeting exposure; low attention; fragmented audiences.
Radio is the wireless transmission of signals, by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. It does not require a medium of transport. Information is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude or their frequency. When radio waves pass an electrical conductor, the oscillating fields induce an alternating current in the conductor. This can be detected and transformed into sound or other signals that carry information.
The Advantages of radio include good local acceptance; high geographic and demographic selectivity; low cost. Its disadvantages include: audio only; fleeting exposure; low attention; fragmented audiences.
However, the advent of satellite radio/Internet radio has brought about a revolution in radio ncommunication.
Internet radio (aka e-Radio) is an audio broadcasting service transmitted via the Internet. Broadcasting on the Internet is usually referred to as webcasting since it is not transmitted broadly through wireless means but is delivered over the World Wide Web. The term “e-Radio” suggests a streaming medium that pre- sents listeners with a continuous stream of audio to which they have no control much like traditional broadcast media. It is not synonymous with podcasting which involves downloading and therefore copy- right issues. Nor does e-Radio suggest “on-demand” file serving. Many Internet “radio stations” are associated with a corresponding traditional “terrestrial” radio station or radio network. Internet-only radio stations are usually independent of such associations.
Conventional radio broadcasting on AM has been around for about a century and on FM, since the 1950s. New digital broadcasting technologies such as DAB, XM radio, DRM and others are becoming very popular in many parts of the world. Traditional on-air radio has many strengths and is still a vibrant me- dium. It is likely that it will remain the principal delivery mechanism of radio content for quite some time.
The Internet has opened up a new possibility for radio enthusiasts.
During the last ten years or so, Internet Radio has been a major focus of technical innovations and opera- tional experiments. Now Internet Radio has become a mature medium with its distinctive characteristics.
There are many tens of thousands of Internet Radio stations worldwide, ranging from big portals down to small local and individual streaming stations. The main assets of Internet Radio are its global reach, interactivity and personalization. While today the users need a computer device and a broadband connec- tion to access Internet radio stations, in future they will be able to enjoy it on a number of portable wireless device. Internet Radio will become ubiquitous.
Tetra : Terrestrial Trunked Radio is a digital cell phone system for military, police and ambulances. Com- mercial services.
Navigation : Moving around (here in and across a medium)
FM : Frequency Modulation VHF : Very High Frequency HF : High Frequency
SW : Short Wave
HZ : Hertz (Unit of frequency)
Radar (Radio Detection And Ranging) detects objects at a distance by bouncing radio waves off them. Emergency Position-Indicating Radio Beacons (EPIRBs) : Small radio transmitters that satellites can use to locate a person or vehicle needing rescue.
Community radio : A type of radio service that caters to the interests of a certain area, broadcasting material that is popular to a local audience but is overlooked by more powerful broadcast groups.
- What are the characteristic features of radio?
- Explain the advantages and disadvantages of traditional
- What is satellite/internet radio? Explain its advantages over traditional
- What is community radio? What are its advantages?
