|Even though Amateur Radio seems to be small part
of radio as we know it today, it was very instrumental in the development of
My interest in radio stems from my childhood days when I would enjoy listening to long-distance broadcast band programs, short wave, and amateur radio on my grandfather's Philco console radio. This is a picture of that very radio. My eternal thanks to my dad for giving me the radio after he inherited the radio from my grandfather. He knew how much I loved radio.
The radio will be 70 years old in 2011!
Also see "More Radio History"
Radio is one of our most important means of communication. It enables people to send words, music, codes, and other signals to any part of the world. People also use radio to communicate far into space.
The most widespread and familiar use of radio is broadcasting. Radio broadcasts feature music, news, discussions, interviews, descriptions of sports events, and advertising. People wake up to clock radios and ride to their jobs listening to automobile radios. They also spend leisure hours hearing their favorite programs on radio.
Radio broadcasting once had much the same entertainment role as television has today. From the 1920's to the early 1950's, millions of families gathered around their radios every night. They listened to dramas, light comedies, variety shows, live music, and other kinds of programs. This period, which is sometimes called the Golden Age of Broadcasting, ended with the rise of television during the 1950's.
Radio has many uses in addition to broadcasting. Airplane pilots, police officers, sailors, and others use radio for quick communication. Scientists send radio waves into the sky to learn about the weather. Telephone companies send messages by radio and by telephone lines. Many people operate amateur radio stations.
Radio works by changing sounds or other signals into radio waves, a kind of electromagnetic wave. These waves travel through the air and through space. They also go through some solid objects, such as the walls of buildings. Radio waves travel at the speed of light--186,282 miles (299,792 kilometers) per second. When they reach a radio receiver, the receiver changes them back into the original sounds.
Many people contributed to the development of radio, and no one individual can be called radio's inventor. Guglielmo Marconi of Italy sent the first radio communication signals in 1895. Today, radio waves that are broadcast from thousands of stations, along with waves from other sources, fill the air around us continuously.
Broadcasting ranks as the most familiar use of radio by far. Every day, millions of people throughout the world listen to radio programs that are broadcast for their entertainment and information. But people also use radio in dozens of other ways. Many uses involve two-way communication, in which radio equipment is used both to send and to receive messages. In broadcasting and most two-way communication, radio transmits sounds, such as voice and music. But in other kinds of uses, radio sends communication signals other than sounds. Such signals include the radio beams used in navigation and the remote control signals used in operating certain kinds of equipment.
The scope of broadcasting. Radio broadcasts originate at radio stations. There is at least one radio station in every country in the world, and altogether there are more than 27,000 stations. The people of the world own about 2 billion radios, or an average of about 1 for every 3 people.
The United States has more radio stations and more radios than any other country. About 11,000 stations operate in the United States, and the American people own about 535 million radios. Thus, the United States has more than a third of the world's radio stations and about a fourth of its radios. Almost every U.S. household has at least one radio, and--on the average--each household has about six. According to one survey, over 80 percent of all American teen-agers and adults listen to radio at least once a day.
A major reason for the widespread use of radios is their portability. Portability means the ability to be carried around easily. Some radios are large and are powered by current from electric outlets. These radios are usually kept in the home, where electricity is readily available. But millions of radios are small, lightweight instruments that are powered by batteries. People listen to these radios almost everywhere--in homes and yards, at beaches and picnics, and even while strolling down the street. Radios are also widely used in automobiles. Nearly all cars made in the United States have a radio.
Portable radios are a convenience in the United States and other places where electricity is readily available. But many homes in some parts of the world have no electricity. In such areas, portable radios provide the people with one of the few links they have to the world outside their own village or town.
Kinds of programs. Radio programming varies from country to country. But in all countries, programs primarily provide entertainment and information. This section describes programming in the United States.
About 90 percent of all programs broadcast in the United States are designed for entertainment. The other 10 percent provide some kind of information. Advertisements are broadcast during and between the programs of commercial stations, which account for about 87 percent of all the stations. Noncommercial stations, also called educational or public stations, do not have commercials.
Radio stations compete with one another for listeners. Most stations program broadcasts to appeal to a specific audience. For example, stations that play rock music try to attract teen-age and young adult listeners.
Entertainment. Recorded music is the chief kind of radio entertainment. Most stations specialize in one kind of music, such as rock, classical, country and western, or "old-time favorites." Some stations broadcast several kinds of music.
Radio stations that broadcast music have disc jockeys who introduce and comment on the music. They play an important role. Each station tries to hire disc jockeys whose announcing styles and personalities appeal to the station's largest audience.
Information. Programs that provide information include newscasts, talk shows, and play-by-play descriptions of sports events.
Newscasts come on the air at regular times--every half-hour or hour on most stations. In addition, radio stations present on-the-spot news coverage of such special events as political conventions, space shots, Senate hearings, and speeches by the President. Radio stations also broadcast such specialized news as weather forecasts, traffic reports, and stock market and agricultural information. Other news features include public service announcements about community events, activities of community groups, and government services. A few stations broadcast only news to serve listeners who prefer news programs to music.
Talk shows present discussions on a variety of topics and interviews with people from many professions. Each show has a host or hostess who leads the discussion or does the interviewing. The subject of a program may be a current political topic, such as an election or a government policy, or it may deal with a social issue, such as crime, pollution, poverty, racism, or sexism. Many talk shows allow listeners to take part in the program. Listeners are invited to telephone the station to ask questions or give their opinions about the topic.
Sports events, like news, have always been an important part of radio programming. Sports announcers try to capture a game's action and excitement for the listeners. Most of the games played by the more than 100 major league baseball, basketball, football, and hockey teams in the United States and Canada are broadcast locally on radio. Radio stations also broadcast many college and some high school sports contests.
Two-way communication is a widespread use of radio. Two-way radio provides communication in an almost endless variety of jobs--whenever there is a need for quick contact between one point and another. Some of the most important of these uses are in (1) public safety, (2) industry, (3) national defense, and (4) private communication.
In public safety. Police officers use radio to help prevent crimes and arrest lawbreakers. Radio also aids fire fighters in controlling and putting out fires. Police officers and fire fighters use two-way radios in their patrol cars and fire engines. They also carry small, portable two-way radios called walkie-talkies. They use these radios to get directions from their headquarters and to communicate with one another. Airplanes and ships use two-way radios for safe operation and for rescue missions.
Special ambulance teams use radio to help save lives after rushing to the scene of an accident. These specialists radio the details of a victim's condition to a doctor in a hospital. The doctor then directs the emergency treatment of the victim by radio.
In industry. Two-way radio has become a standard tool of the transportation industry, from taxicabs to jet airliners. Taxi drivers receive radioed instructions on where to pick up customers. Airplane pilots get landing and take-off directions by radio. Ships, trains, and numerous trucks are equipped with two-way radios.
Radio also helps save time, money, and work in many other industries. Construction workers use it to communicate from street level to the top of a skyscraper. With the aid of two-way radio, farmers, ranchers, and lumber workers receive information when they need it and get equipment delivered where they want it.
In national defense. Radio plays a key role by linking defense units around the world. All branches of the armed services depend heavily on two-way radio communication. Military personnel use radio equipment in planes and tanks and on ships. Large communications centers and handy walkie-talkies help provide instant contact between military units.
In private communications. Many licensed radio operators called hams send and receive long-distance messages by radio as a hobby know as Amateur Radio. Children play with walkie-talkies that broadcast short distances. Many people use two-way radios in such places as cars and pleasure boats. Radio used by private citizens for short-distance communication is called citizens band radio. The development of cellular radio during the 1980's made it possible to use personal telephones in automobiles.
Radio waves can carry many more kinds of information than just sounds. Many important radio jobs involve the sending and receiving of various kinds of signals. Such signals make possible the operation of navigational aids, remote control devices, and data (information) transmission equipment. In addition, radio has several highly specialized uses.
Navigation. Radio beams made up of special navigation signals help airplane pilots stay on the proper flying course. Many ships have devices for mapping their position with the aid of navigation signals that are radioed from shore. Airplanes and ships also rely on radar--a special form of radio--for their safe operation. In addition, radio-assisted navigational devices help astronauts guide their spacecraft exactly to their destination.
Remote control by radio can be used to guide the flight of a model airplane or a real plane that has no pilot. Radio-controlled devices also direct railroad cars in switching yards. In addition, radio-controlled devices do such jobs as opening garage doors or changing television channels.
Data transmission. Radio equipment can send information in much larger quantities and at much greater speeds than any person can. Data transmission usually occurs between one electronic device and another. An example of data transmission is the sending of information from radio equipment on the ground to a computer in a spacecraft. Radio is also used to send electronic mail. Messages are converted into electronic signals, which are then transmitted by radio.
Special uses. Spies use hidden radio devices called bugs to listen in on conversations in attempts to learn secret information. Doctors sometimes use radio to help them diagnose stomach illnesses. The patient swallows a radio pill--also called a capsule radio--that consists of a miniature radio transmitter enclosed in a capsule. While inside the stomach, the radio pill transmits signals that provide the doctor with medical information about the patient. Certain kinds of radio waves have so much energy that people can use them to cook their food. Radio waves cook food in microwave ovens.
The sending and receiving of radio communications involve three general steps: (1) creating the communication signals and changing them into radio waves, (2) transmitting (sending) the radio waves, and (3) receiving the radio waves and changing them into a form that can be understood. The following two sections--How radio programs are broadcast and How radio programs are received--describe the steps in radio broadcasting.
Radio stations are places where radio broadcasts begin. Many stations are located in office buildings. The heart of a radio station is the studio.
The studio is the part of the radio station from which programs are broadcast. It is soundproofed so that no outside sounds can get in and interfere with the broadcasts. Many studios have two separate areas--the main studio and the control room. The main studio is the place where the performers do their jobs. The control room contains the equipment needed to prepare and broadcast programs. This equipment includes the control board, a panel with the switches, gauges, dials, and other devices used to regulate the sounds of the broadcasts. A large window in the wall between the main studio and the control room allows people in each area to see one another.
Putting a show on the air involves such jobs as script writing, announcing, and controlling the broadcasting equipment. At a small station, the same person may write scripts, announce, play recordings, and even operate the controls. A large station has a staff that plans programs, including the writing of news and other scripts. Once the program goes on the air, the announcer reads a script or simply adlibs (speaks without a script).
During the Golden Age of Broadcasting, the production of some radio programs was a complex process involving many people. Writers wrote scripts for comedies, dramas, and variety shows. A director guided actors and actresses, who stood around a microphone reading their lines. An announcer introduced the show, closed it, and read the commercials. Sound-effects specialists created such sounds as thunder, footsteps, creaking doors, and galloping horses. An orchestra played appropriate music. Many radio shows were performed live on a stage of a theaterlike studio in front of an audience.
Today, the production of most radio programs is much less complicated than it was during the Golden Age. Most programs consist of conversation and prerecorded music. In addition, many radio stations are becoming automated. Computers do much of the work formerly done by people, such as operating technical equipment, recording program information, preparing and sending bills, and even running the control board. Automation saves money by reducing the number of employees needed to run the station. It also allows the station's personnel to concentrate on more creative tasks.
From sound waves to electric waves. A radio program consists of speech, music, and other sounds. These sounds are either live or prerecorded. Live sounds are broadcast at the same time they are produced. They include the words spoken by announcers. They also include sounds that come from a remote location, such as a ballpark. Prerecorded sounds are not broadcast when first produced. They are stored on phonograph records, tapes, or audio compact discs (CD's) and broadcast later. Almost all the music and most commercials heard on radio are prerecorded.
To understand how radio broadcasting works, it is necessary to know what sound is. All sounds consist of vibrations. The number of vibrations each second is the frequency of the sound. For example, the sound of a person's voice consists of vibrations of the air that are caused by the person's vibrating vocal cords. The faster the vocal cords vibrate, the higher the frequency. The slower the vocal cords vibrate, the lower the frequency. Sound travels through the air in the form of waves called sound waves.
During a live radio broadcast, a microphone picks up speech and other sounds that make up the program. When sound waves enter the microphone, they cause an electric current that runs through the microphone to vary. The variations in the electric current form audio-frequency waves that match the program's sound waves. Prerecorded sounds are also changed into audio-frequency electric waves before being broadcast.
From electric waves to radio waves. The electric waves representing the live and prerecorded sounds of the program travel over wires to the control board. A technician uses the control board to select, adjust, and mix the material to create the program signal that will be broadcast. The program signal travels from the control board to the transmitter, usually over wires.
Low-power transmitters may be located in the studio. High-power transmitters are generally located far away from the studio, at the site of the transmitting antenna (the device that radiates, or sends, radio waves through the air). A special beam of radio waves called microwaves is sometimes used to send the program signal from the studio to a distant transmitter.
In the transmitter, the program signal is combined with electric waves called radio-frequency waves. Radio-frequency waves have a much higher frequency than do the audio-frequency waves that make up the program signal. Radio-frequency waves are also known as carrier waves because they "carry" the program signal away from the transmitter to radios. The frequency of the carrier waves produced in the transmitter is the radio station's broadcast frequency--that is, the frequency to which a radio must be tuned to hear that station.
Transmitting radio waves. After the program signal is combined with the carrier waves, the transmitter amplifies (strengthens) the combined radio signal and sends it to the antenna. The antenna then broadcasts the radio signal through the air.
Radio waves travel at the speed of light. This speed is 186,282 miles per second (299,792 kilometers per second). By contrast, sound waves move through the air at the speed of only about 1/5 mile per second (0.3 kilometer per second). This great difference in speed can cause surprising effects. Imagine a live radio broadcast of a concert taking place in New York City. The music would actually be heard by radio listeners in California a fraction of a second sooner than by the audience sitting in the back of the concert hall.
Kinds of broadcast waves. A radio broadcast is transmitted in one of two ways, depending on how the carrier waves and program signal are combined. These two kinds of radio transmission are amplitude modulation (AM) and frequency modulation (FM). In AM transmission, the amplitude (strength) of the carrier waves is varied to match changes in the program signal coming from the radio studio. In FM transmission, the amplitude of the carrier waves remains constant. But the frequency of the carrier waves is varied to match changes in the program signal sent from the studio.
An antenna sends out two kinds of AM radio waves--ground waves and sky waves. Ground waves spread out horizontally from the transmitting antenna. They travel through the air along the earth's surface and follow the curve of the earth for a short distance. Sky waves spread up into the sky. When they reach a layer of the atmosphere called the ionosphere, or the Kennelly-Heaviside layer, they are reflected back down to earth. This reflection enables AM broadcasts to be received by radios far away from the antenna.
An FM radio antenna sends out waves that travel in the same directions as AM waves, but FM waves that go skyward are not reflected. Instead, they pass through the atmosphere and go into space. The FM waves that spread horizontally travel in what is called line-of-sight. This means that FM waves cannot be received farther than the horizon as seen from the antenna. AM broadcasts can be received at much greater distances than FM broadcasts because AM signals bounce off the atmosphere and reach beyond the curve of the earth. Although their range is limited, FM broadcasts have an important advantage over AM broadcasts. FM programs are not affected by static as much as AM programs are. FM transmission also produces a much truer reproduction of sound than does AM.
Broadcasting power and frequency. Another factor that influences the distance a radio program can be broadcast is the power of the transmitter. The strongest AM stations have a power of 50,000 watts. They can be heard far away, especially at night when sky waves are especially effective. For example, 50,000-watt stations in Chicago can be heard at night by listeners in Florida, about 1,000 miles (1,600 kilometers) away. The weakest AM stations operate at 250 watts and usually serve only one or two towns. The power of FM stations ranges from 100 watts, which can broadcast about 15 miles (24 kilometers), to 100,000 watts, which can broadcast about 65 miles (105 kilometers). Some noncommercial FM educational stations operate at as little as 10 watts and reach an area of only a few miles or kilometers.
Each station broadcasts on a different channel, or assigned frequency. The use of different frequencies keeps stations from interfering with one another's broadcasts. Frequency is measured in units called hertz (vibrations per second). One kilohertz equals 1,000 hertz, and one megahertz equals 1,000,000 hertz. The AM band (group of frequencies) extends from 535 to 1,705 kilohertz. The FM band extends from 88 to 108 megahertz.
Radios pick up radio-frequency signals, separate the program signals from the carrier waves, and then change the program signals into sound waves. Different types of radios can receive different broadcast bands. Many radios can receive AM and FM, the most popular broadcast bands. Multiband radios can pick up AM, FM, and other bands, such as police, marine, aviation, and short-wave bands.
One of the simplest radio receivers is the crystal radio. This type of receiver uses an electronic device called a crystal rectifier to detect changes in the strength of an AM signal. These changes in signal strength represent the program's original sound waves. A crystal radio works on just the power of the radio waves it receives and needs no electric power source. However, a listener must use earphones because a crystal radio can produce sound only at a very low volume. Furthermore, this type of radio does not receive FM broadcasts well. Because of these limitations, most radios made today are electrically powered.
The electric power for the radio can come from batteries or from an electrical outlet in a house or other building. A typical radio that runs on household power has a part called a power transformer that lowers the household voltage to the level the radio requires.
The main parts of an electrically powered radio include (1) the antenna, (2) the tuner, (3) the intermediate-frequency amplifier and detector, (4) the audio-frequency processor and amplifier, and (5) the speaker. A radio that can receive both AM and FM signals also has a switch for selecting the band.
The antenna is a length of wire or a metal rod that picks up radio waves. The antenna may be entirely inside the radio, or part of the antenna may be outside the radio and connected to it, as is the case in automobile radios. When radio waves strike the antenna, they produce extremely weak electric waves in it. However, an antenna receives radio waves from many stations at the same time. In order to hear a single program, a listener must tune the radio to the desired station.
The tuner is the part of the radio that makes it sensitive to particular frequencies. A display on the radio shows the frequencies, or channels, of the stations that may be tuned in. For example, station WQAM in Miami, Florida, broadcasts on a frequency of 560 kilohertz. To tune in WQAM, a listener selects number 560 (abbreviated as 56 or 5.6 on some radio displays).
Today, most radio receivers use the superheterodyne circuit design. In a superheterodyne radio, the tuner converts the carrier-frequency part of any incoming radio signal to a single lower frequency. This lower frequency, which is called an intermediate frequency, is usually 10.7 megahertz for the FM band and 455 kilohertz for the AM band. The use of a single intermediate frequency simplifies the radio's design and improves the radio's selectivity--that is, its ability to pick a desired radio signal from among the many received by the antenna.
The tuner of a superheterodyne radio consists of three main parts: (1) a variable capacitor or a quartz crystal oscillator, (2) a local oscillator, and (3) a converter. The external tuning control is connected to either a variable capacitor or, in newer, more advanced radios, a quartz crystal oscillator. When a listener adjusts the tuning control, these devices change the frequency of the local oscillator. The local oscillator determines which station the radio receiver picks up, and so a change in its frequency causes a new station signal to be selected. The converter changes the selected radio-frequency signal to an intermediate-frequency signal.
The intermediate-frequency amplifier and detector receive the intermediate-frequency signal produced by the tuner. The amplifier strengthens the signal, which then enters the detector. The detector removes the intermediate frequency from the signal and leaves only the audio frequency--the part that represents the program.
The audio-frequency processor and amplifier strengthen the audio-frequency part of the signal. Volume, bass, and treble controls can adjust the loudness and tone of the sound before it goes to the speaker.
The speaker is the final link between the broadcasting studio and the listener. It changes the electric signal back into the original program sounds. The basic parts of a speaker are a magnet and a coil of wire called the voice coil. The voice coil is attached to a cone, which is usually made of paper. The electric current from the amplifier passes through the coil and exerts varying push and pull against the magnet's field. The cone vibrates in time with the electric current flowing through the coil. The cone's vibrations create sound waves like those that first went into the microphone, and the original program sounds come out of the radio.
Stereophonic receivers can detect stereophonic, or stereo, multiplex signals. These signals are formed by sending two separate audio-frequency signals on a single carrier frequency at the same time. The two audio-frequency signals are called the right channel and the left channel. Stereo multiplex signals better re-create the sensation of hearing live sounds than do monophonic signals, which transmit only one channel.
Both stereo and monophonic receivers have a super-heterodyne circuit. However, stereo receivers have an additional circuit called a demultiplexer. This circuit changes the multiplex signal back into its original left and right channels. The two parts of the signal then enter separate audio-frequency processors and amplifiers. Stereo receivers have at least two speakers, one for each channel.
Radio has several important industrial roles. Broadcasting stations provide jobs for thousands of workers across the country. Radio commercials help other businesses sell every kind of product--from dog food to automobiles to houses. The recorded music played by disc jockeys is probably the most important factor affecting the sale of tapes and CD's. Stores throughout the United States sell millions of radio receivers each year.
Stations and networks. More than 11,000 radio stations operate in the United States. Most of these are commercial radio stations, almost all of which are privately owned businesses. The United States also has many educational stations. Most of these nonprofit organizations are operated by colleges and universities. A radio station may employ only a few workers or as many as several hundred.
Commercial radio stations broadcast programs to attract listeners. The stations sell broadcasting time to advertisers who want to reach these listeners. Sponsors pay the stations for time during and between the programs to advertise their products. In the United States, sponsors spend billions of dollars a year on radio advertising. Stations that attract the largest audiences receive the highest fees.
Many commercial stations have an affiliation (working agreement) with a national network. A network is an organization that provides some of the programming for its affiliated radio stations. It also sells some of the stations' advertising time. Networks send radio signals to their affiliates through communications satellites.
There are a number of nationwide networks in the United States. The largest of these networks include the ABC Radio Networks, a division of Capital Cities/ABC Incorporated; the CBS Radio Division of CBS, Inc.; USA Network; and Westwood One, Incorporated. Westwood One, the largest of the nationwide networks, owns the NBC Radio Networks and the Mutual Broadcasting System (MBS). Several regional networks also operate in the United States. A regional broadcasting network is one that serves radio stations within a certain part of the country.
Careers. The radio industry offers a variety of career opportunities. Stations and networks need program planners and announcers, news reporters and newscasters, technicians, and maintenance workers. Other personnel write scripts, sell advertising time, and work in such general business activities as accounting and public relations. An employee of a small radio station may be called on to do any of these jobs at one time or another. Therefore, a job with a small station provides excellent experience for a person starting a radio career. Most people who hold a key job at a large station first gained experience by working at small stations.
Employees of large stations or networks generally specialize in one of four kinds of work. These are (1) programming, (2) engineering, (3) sales, or (4) general administration.
The programming department is headed by a program director. This department includes journalists who gather the news and write news reports and other material to be broadcast. Announcers, copywriters, and production personnel also belong to the programming department. The engineering department includes technicians who operate and maintain the broadcasting equipment. Members of the sales department are responsible for selling broadcasting time to sponsors. The general manager of the station or network heads the department of general administration and has overall responsibility for the organization's operation. The general administration department also includes accountants, secretaries, typists, and other general office workers.
More than 300 colleges and universities in the United States offer courses in broadcasting. These courses deal with both radio and television broadcasting. Many of the broadcasting companies include both radio and television stations, and some of the employees of these companies work in both fields. Information on careers in radio broadcasting can be obtained from the National Association of Broadcasters in Washington, D.C.
Careers outside of broadcasting are available to people trained in the operation and repair of radio equipment. Many people skilled in radio repair go into business for themselves.
The government of every country regulates the use of radio in some way. One reason for regulation is the need to maintain order among users of radio channels. Without such regulation, radio stations and other radio users would broadcast signals that would interfere with one another and make it impossible for communications to be understood. Many governments also regulate radio for another reason. They want radio to be used to promote their own ideas and policies. They also want to be able to prevent the broadcast of ideas that government leaders oppose.
The United States. The Federal Communications Commission (FCC) regulates all nonmilitary communication by radio within the United States. The FCC assigns frequencies and call letters for various types of radio operations, including broadcasting, amateur radio operation, and marine and aviation radio. In addition, the FCC issues licenses to stations and certain other users of transmitting equipment.
The FCC does not censor radio programs. But it can impose a fine on or revoke the license of a station that violates broadcasting rules. Also, the FCC does not tell stations what programs they should broadcast. Every station must apply to the FCC every seven years to have its license renewed.
The United Kingdom. Most radio stations in the United Kingdom are owned by the government. The British Broadcasting Corporation (BBC) regulates these stations and also provides their programs. The BBC falls under the jurisdiction of the British government. But it has been organized to operate independently, without political interference. The first British radio stations operated by private citizens began broadcasting in 1973. The Radio Authority, a government agency, regulates these stations.
Canada. Canada also has both government-owned and private radio stations. The Canadian Broadcasting Corporation (CBC) provides the programs for the government stations. The Canadian Radio-television and Telecommunications Commission supervises government and private stations. Its functions resemble those of the Federal Communications Commission in the United States.
Other countries. A large number of countries, including Australia and New Zealand, have both private and government-owned stations, as do Canada andthe United Kingdom. In most other countries, the government owns all the stations. The United States is the only nation in which the federal government does not control any radio stations that broadcast to the general public within the country.
In general, a country allows radio broadcasters the same degree of freedom it allows its citizens. Most democratic countries allow wide freedom in broadcasting. Many totalitarian governments severely regulate and censor broadcasting for political purposes.
The development of radio in the late 1800's revolutionized communication. At that time, people had two other means of quick, long-distance communication-- telegraph and telephone. But the signals sent by both these devices had to travel through wires. As a result, telegraph and telephone communication was possible only between places that had been connected by wires. Radio signals, on the other hand, passed through the air. Therefore, radio enabled people to communicate quickly between any two points on land, at sea, and-- later--in the sky, and even in space.
Radio broadcasting, which began on a large scale during the 1920's, caused major changes in the everyday lives of people. It brought a tremendous variety of entertainment into the home for the first time. It also enabled people to learn about news developments as they happened or shortly afterward.
Early development. Radio, like many other inventions, developed from the theories and experiments of many people. Joseph Henry, a professor at the College of New Jersey (now Princeton University), and a British physicist, Michael Faraday, discovered one of the first important ideas in the early 1830's. Henry and Faraday had experimented with electromagnets. Working separately, they each developed the theory that a current in one wire can produce a current in another wire, even though the wires are not connected. This idea is called the induction theory. In 1864, James Clerk Maxwell, another British physicist, helped explain the induction theory by suggesting the existence of electromagneticwaves that travel at the speed of light. In the 1880's, the German physicist Heinrich Hertz performed experiments that proved Maxwell's theory to be correct.
In 1895, Guglielmo Marconi, an Italian inventor, combined earlier ideas and his own ideas and sent the first radio communication signals through the air. He used electromagnetic waves to send telegraph code signals a distance of more than 1 mile (1.6 kilometers). In 1901, Marconi's radio equipment sent code signals across the Atlantic Ocean from England to Newfoundland.
During the early 1900's, electrical engineers developed various kinds of vacuum tubes that could be used to detect and to amplify radio signals. Lee De Forest, an American inventor, patented a vacuum tube called a triode, or audion, in 1907. This tube became the key element in radio reception.
There are many claims for the first broadcast of human speech over the air. Most historians give credit to Reginald A. Fessenden, a Canadian-born physicist. In 1906, Fessenden spoke by radio from Brant Rock, Massachusetts, to ships offshore in the Atlantic Ocean. The American inventor Edwin H. Armstrong did much to improve radio receivers. In 1918, he developed the superheterodyne circuit. Later, in 1933, he discovered how to make FM broadcasts.
The first practical use of the "wireless," as radio was then called, was for ship-to-ship and ship-to-shore communication. Radio helped save the lives of thousands of victims of sea disasters. The first sea rescue involving the use of radio took place in 1909, after the S.S. Republic collided with another ship in the Atlantic Ocean. The Republic radioed a call for help that brought rescuers who saved almost all the passengers. Radio also aided in the rescue of the survivors of the famous Titanic shipwreck in 1912.
Dozens of new uses were soon found for radio. By the 1930's, airplane pilots, police, and military personnel were using radio for quick communication.
The start of broadcasting. Experimental radio broadcasts began about 1910. In that year, Lee De Forest produced a program from the Metropolitan Opera House in New York City. The program starred the famous singer Enrico Caruso. An experimental radio station opened at the University of Wisconsin in Madison in 1915, and another began operating in Wilkinsburg, a suburb of Pittsburgh, Pennsylvania, in 1916.
Many people consider radio station WWJ, in Detroit, the first commercial radio station. It began regular broadcasts on Aug. 20, 1920. Others claim the distinction for station KDKA in Pittsburgh. KDKA grew out of the Wilkinsburg experimental station that began in 1916. Its starting date as a regular broadcasting station is uncertain. But the station's broadcast of the 1920 presidential election results on Nov. 2, 1920, is generally considered the beginning of professional broadcasting. The first license to broadcast regularly went to station WBZ in Springfield, Massachusetts. The federal government issued the license on Sept. 15, 1921.
Stations soon sprang up in all parts of the United States. Network broadcasting began as early as October 1922. At that time, WJZ in New York City and WGY in Schenectady, New York, broadcast the World Series. The two stations formed a simple network. The stations were connected by telephone lines. Network broadcasting--or, as it was called, chain broadcasting--soon included stations across the United States. The Radio Corporation of America (RCA) formed the National Broadcasting Company (NBC), which was the first permanent national network, in 1926.
The Golden Age of Broadcasting began about 1925 and lasted until the early 1950's. During this period, radio was a major source of family entertainment. Every night, many families gathered in their living rooms to listen to comedies, action-packed adventure dramas, music, and other kinds of radio entertainment. Children hurried from school to hear afternoon adventure shows designed for them. In the daytime, millions of womenlistened to dramas called soap operas because soap manufacturers sponsored many of them.
Radio's famous comedians included Fred Allen, Jack Benny, Eddie Cantor, and Bob Hope. The ventriloquist Edgar Bergen and his dummy, Charlie McCarthy, hosted a weekly comedy program with famous stars as guests. Situation comedies included the "Amos 'n' Andy" show, starring Freeman Gosden as Amos and Charles Correll as Andy; and the "Fibber McGee and Molly" show, featuring the husband-and-wife team of Jim and Marian Jordan. The husband-and-wife comedy team of George Burns and Gracie Allen also gained fame in radio. Other comedies included "The Great Gildersleeve," "Duffy's Tavern," "Henry Aldrich," and "Our Miss Brooks."
Radio also brought to the home the music of every famous band leader, including Tommy Dorsey, Duke Ellington, Benny Goodman, Harry James, Guy Lombardo, and Glenn Miller. Exciting radio dramas included "Buck Rogers in the 25th Century," "Gangbusters," "The Green Hornet," "Inner Sanctum," "Jack Armstrong, the All-American Boy," "The Lone Ranger," "The Shadow," and "Superman." Some radio soap operas were "The Guiding Light," "John's Other Wife," "Just Plain Bill," "Ma Perkins," "One Man's Family," "Our Gal Sunday," and "Stella Dallas."
The popularity of the "Amos 'n' Andy" show and the impact of a program called The War of the Worlds help illustrate the enormous influence radio entertainment had on people. "Amos 'n' Andy," perhaps the most popular radio program of all time, was broadcast each weekday throughout the 1930's. While this program was being broadcast--from 7:00 to 7:15 p.m. Eastern Standard Time--many movie theaters stopped their films and turned on radios so the audiences could listen to the program. Some stores and restaurants played radios over public address systems so that customers would not miss it. The actors and actresses on the "Amos 'n' Andy" show were whites who portrayed blacks. Many people have criticized the program for portraying African Americans as a stereotyped group to be laughed at.
The War of the Worlds, broadcast on Oct. 30, 1938, was one program in a series of dramas put on by Orson Welles' Mercury Theater on the Air. The program, adapted from the science-fiction novel of the same name by the British author H. G. Wells, took the form of on-the-spot news reports describing an invasion of New Jersey by aliens from Mars. The announcer told the radio audience that the show was fictional. Even so, large numbers of listeners believed the invasion was actually taking place, and widespread panic resulted. Thousands of people called the police and other authorities for instructions on what to do. Many people fled their homes, some taking furniture with them. Still others were treated in hospitals for shock.
Some radio news reporters of the Golden Age became almost as well known as the top entertainers. They included Elmer Davis, Gabriel Heatter, H. V. Kaltenborn, Fulton Lewis, Jr., Edward R. Murrow, Lowell Thomas, and Walter Winchell. Newscasts became especially important during World War II (1939-1945). Millions of Americans turned to radio for the latest war news every day. The governments of countries that fought in the war made widespread use of broadcasts to their own and other countries for propaganda purposes. The Voice of America, an agency of the United States government, began broadcasting overseas in 1942 to inform the world of America's role in the war.
Franklin Delano Roosevelt, President of the United States from 1933 to 1945, used radio very effectively. Roosevelt held informal talks called fireside chats. The talks did much to help Roosevelt gain support for his policies. Earlier Presidents, beginning with Woodrow Wilson in 1919, had spoken on radio. But Roosevelt was the first to fully understand the great force of the medium and the opportunity it provided for taking government policies directly to the people.
Broadcasting today. The rise of television in the 1950's ended the Golden Age of radio broadcasting. People turned to TV for comedies, dramas, and variety shows, and these kinds of shows all but disappeared from radio. Many people believed television would cause radio broadcasting to become an unimportant communication medium with a very small audience. Instead, radio's audience has continued to grow, in spite of competition from television. In 1952, at the end of the Golden Age, Americans owned about 105 million radios. Today, they own about 550 million, or about 5 times as many as in 1952.
There are several reasons for radio broadcasting's continued growth. After the Golden Age of Broadcasting, music became the major form of radio entertainment. Rock music--which was a new form of music in the 1950's--became an important kind of music on radio. Broadcasts of rock music gained many listeners--especially teen-agers--for radio. There are also many other kinds of music on radio. Lovers of all kinds of music can turn to radio to hear their favorite recordings.
Other developments in programming have helped gain listeners for radio. These developments include talk shows and stations that broadcast only news. An important feature of such programs is their thorough coverage of a topic or news events.
Another reason why radio broadcasting has continued to grow is the increased popularity of portable radios. Portable radios have made radio a source of personal, rather than family, enjoyment. Automobile radios have also shown a dramatic growth. In 1952, about half of all American automobiles had radios. Today, nearly all the cars made in the United States have radios.
The increasing popularity of FM broadcasts has also contributed to the growth of the radio industry. FM's better sound quality enabled it to surpass AM in popularity in the late 1970's.
Still another aid to radio's growth has been the development of stereophonic broadcasting. Stereo broadcasts began on a large scale in 1961, when the FCC allowed only FM stations to broadcast in stereo to help them compete with AM stations. The FCC authorized AM stereophonic broadcasting in 1982.
In the late 1980's and early 1990's, researchers developed digital audio broadcasting (DAB), a new type of radio signal processing. The introduction of DAB, which was scheduled for the late 1990's, would provide sound of the same high quality as that from an audio compact disc.