Birth of the BBC

Heinrich Hertz’s name has been given to the cycle per second (hertz, Hz), with 1 kilohertz (kHz) being 1,000 cycles per second, and 1 megahertz (MHz) being 1 million cycles per second. Low and medium frequencies (30 to 3,000 kHz) are used by radio broadcasters transmitting on those parts of the spectrum traditionally described as long or medium wave, and most early transmissions in Europe and the United States were solely of this type. Because electromagnetic waves in a uniform atmosphere travel in straight lines and because the Earth’s surface is approximately spherical, long-distance radio communication is made possible by the reflection of radio waves from the Earth’s ionosphere. This allows programmes to be received both nationally and beyond national borders. However, these frequencies tend only to be able to use reflection from the ionosphere to bounce round the Earth’s curvature under night-time atmospheric conditions, thus creating the possibility of each radio station covering a much wider area, but simultaneously contributing to increased interference between rival signals.

Transmitters

Essential components of a radio transmitter include an oscillation generator for converting commercial electric power into oscillations of a predetermined radio frequency; amplifiers for increasing the intensity of these oscillations while retaining the desired frequency; and a transducer for converting the information to be transmitted into a varying electrical voltage proportional to each successive instantaneous intensity. For sound transmission a microphone is the transducer; for picture transmission the transducer is a photoelectric device.

Other important components of the radio transmitter are the modulator, which uses these proportionate voltages to control the variations in the oscillation intensity or the instantaneous frequency of the carrier, and the antenna, which radiates a similarly modulated carrier wave. Every antenna has some directional properties, that is, it radiates more energy in some directions than in others, but the antenna can be modified so that the radiation pattern varies from a comparatively narrow beam to a comparatively even distribution in all directions; the latter type of radiation is employed in broadcasting.

The particular method of designing and arranging the various components depends on the effects desired. The principal criteria of a radio in a commercial or military aircraft, for example, are lightness of weight and intelligibility; cost is a secondary consideration, and fidelity of reproduction is entirely unimportant. In a commercial broadcasting station, on the other hand, size and weight are of comparatively little importance; cost is of some importance; and fidelity is of the utmost importance, particularly for FM stations; rigid control of frequency is an absolute necessity. In the United States, for example, a typical commercial station broadcasting on 1,000 kHz is assigned a bandwidth of 10 kHz, but this width may be used only for modulation; the carrier frequency itself must be kept precisely at 1,000 kHz, for a deviation of one-hundredth of 1 per cent would cause serious interference with even distant stations on the same frequency.

FM and AM Transmission

“FM” stands for “frequency modulation”, as opposed to “AM”, or “amplitude modulation”. Both terms apply to techniques for imposing a meaningful pattern of variations on an otherwise unvaried stream of energy during transmission, but they have also come to be applied to whole categories of broadcast radio.

AM modulates the carrier radio wave by varying the amplitude (strength of the wave) in accordance with the variations of frequency and intensity of a sound signal, such as a musical note. Such modulation is vulnerable to electrical interference, and the sound quality is variable. Throughout the first half of the century, most standard radio broadcasting was achieved using this technique, and today some music and a great deal of speech radio, which does not necessarily demand high-quality reception, is still found on the AM dial.

FM works by varying the frequency of the carrier wave within a narrowly fixed range at a rate corresponding to the frequency of a sound signal. It is used within the VHF band, so that the terms “VHF” and “FM” have become synonymous for most radio listeners. FM reaches only to the horizon, so a transmitter’s remit is local rather than national in scale. This geographical restriction has the advantage of reducing interference, and coverage is therefore more stable, day or night. The signal itself is inherently static-free, unlike that for AM, and a suitable receiving-set can take advantage of its more generous frequency range and dynamic range to reproduce high-fidelity sound.

FM’s quality advantage over AM, exaggerated further with the development of stereo, has proved particularly suitable for the broadcasting of music and explains the rapid growth in the number of FM stations—often associated with rock and pop—in the 1960s, 1970s, and 1980s (see Sound Recording and Reproduction).

Radio Formats

Music radio—often the most unobtrusive output of all—is now the dominant form of programming across the world, but it is not the only one and it has not always been thus. When the BBC began broadcasting in Britain in the 1920s it established a pattern of mixed programming. The output of a single station or service embraced a wide range of music, comedy, features, talks, drama, religion, sport, and news.

Even when the BBC first offered listeners a choice between two networks (the National Programme and the Regional Programme), both carried mixed programming, with very little difference in content or tone. The range of programmes offered over the course of each day and week catered for different social needs (education, information, or entertainment) and for different sectional interests (such as children, workers, or women), all within one network.

Talk Radio

Relatively few radio stations consist entirely of news. News-gathering is labour-intensive and therefore expensive, and audience ratings are likely to be lower than is the case with music formats. In any case, most stations that concentrate on news often include in their schedules a large element of topical discussion, often with listeners themselves. This form of programming has become a format in itself, and is now more popular than news.

Talk radio, which occurs most often on AM stations, combines interviews and feature material with lengthy phone-ins from listeners. For broadcasters, such programmes are not only cheap to run, they also help to create the impression of radio as a two-way medium, and suggest that a station—particularly a local station, where a sense of shared interests in the audience can be more tangible—is in touch with its listeners. In America in the 1980s, talk radio emerged as an important public forum in the black and Hispanic communities, and the format is now extremely common in local and community radio.

Commercial Radio

Commercial radio, on the other hand, seeks to deliver sizeable audiences of consumers to those advertisers and sponsors who provide its income. It will tend to favour popular programmes over those which might appeal only to a minority, and will target heavily populated rich markets rather than thinly populated poorer markets. Commercial radio may also, however, develop very specialized formats, such as jazz or classical music, in order to capitalize on relatively small but high-spending niche markets. Output is characterized by aggressive marketing, and slick, image-conscious presentation.