Radio

F

Digital Broadcasting

Both AM and FM radio depend on traditional analogue technology, where the signal consists of a continuously changing pattern corresponding to the continuous flow of sound captured by a microphone. Such signals are inherently vulnerable to all sorts of distortions which restrict their ability to carry information without degradation. Digital processing, which breaks a signal down into a stream of individual energy pulses assigned a binary code, can resist distortion and convey far more information. Most large-scale radio broadcasters are now developing digital audio broadcasting, which promises a quality of sound equivalent to that of a CD, and an increase in the number of radio services available within the existing electromagnetic spectrum.

G

Receivers

The technology of the radio receiving-set has also changed dramatically since the origins of broadcasting. The first commercially available radio receivers were crystal sets, which required headphones. They soon gave way to valve receivers with loudspeakers, which enabled people to listen in groups. Growing demand led to larger-scale production of valve receivers, and the price of sets dropped throughout the 1930s.

Even so, the wireless valve remained a relatively expensive item to replace, consumed much primary power, and meant large and cumbersome sets. In 1948 the first manufactured transistor revolutionized reception. It allowed radios to be built that were more reliable, used far less power, and, crucially, were much smaller and cheaper. Transistor radios were mobile in a way that the television sets of the 1950s and 1960s could never be.

The essential components of a modern radio receiver are: (1) an antenna for receiving the electromagnetic waves and converting them into electrical oscillations; (2) amplifiers for increasing the intensity of these oscillations; (3) detection equipment for demodulating; (4) a speaker for converting the impulses into sound waves audible to the human ear (and in television a picture tube for converting the signal into visible light waves); and (5) in most radio receivers, oscillators to generate radio-frequency waves that can be mixed with the incoming waves.

The incoming signal from the antenna, consisting of a radio-frequency carrier oscillation modulated by an audio-frequency or video-frequency signal containing the impulses, is generally very weak. The sensitivity of some modern radio receivers is so great that if the antenna signal can produce an alternating current involving the motion of only a few hundred electrons, this signal can be detected and amplified to produce an intelligible sound from the speaker. Most radio receivers can operate quite well with an input from the antenna of a few millionths of a volt. The dominant consideration in receiver design, however, is that very weak desired signals cannot be made useful by amplifying indiscriminately both the desired signal and undesired radio noise. Thus, the main task of the designer is to assure preferential reception of the desired signal.

Most modern radio receivers are of the superheterodyne type in which an oscillator generates a radio-frequency wave that is mixed with the incoming wave, thereby producing a radio-frequency wave of lower frequency; the latter is called intermediate frequency. To tune the receiver to different frequencies, the frequency of the oscillations is changed, but the intermediate frequency always remains the same (at 455 kHz for most AM receivers and at 10.7 MHz for most FM receivers). The oscillator is tuned by altering the capacity of the capacitor in its tank circuit; the antenna circuit is similarly tuned by a capacitor in its circuit.

One or more stages of intermediate-frequency amplification are included in all receivers; in addition, one or more stages of radio-frequency amplification may be included. Auxiliary circuits such as automatic volume control (which operates by rectifying part of the output of one amplification circuit and feeding it back to the control element of the same circuit or of an earlier one) are usually included in the intermediate-frequency stage. The detector, often called the second detector (the mixer being called the first detector), is usually simply a diode acting as a rectifier, and produces an audio-frequency signal. FM waves are demodulated or detected by circuits known as discriminators or radio-detectors that translate the varying frequencies into varying signal amplitudes.

IV

Radio as a Medium

A

Advantages of Radio

With the growth of television after World War II, many broadcasters predicted the complete demise of radio. A reliance on sound, when images were available, seemed an anachronism. In time, it became apparent that the medium had many unique characteristics that helped distinguish it from both the press and television. Some of these characteristics seem more like limitations, but many can also be turned to the medium’s advantage.

A

1

Imagination

Radio is a “blind” medium, and the type of programmes it produces is derived largely from the simple fact that, unlike television, it provides no visual message to the listener. Radio programmes, unlike the printed pages of books or newspapers, are also ephemeral products: very few people bother to record radio programmes, so they cannot be so easily “re-read”.

Radio programmes therefore have to provide the listener with extra auditory clues to compensate for the lack of images, and must ensure that these clues are understood by the listener at the first—and almost certainly only—hearing. Programme-makers often claim that these difficulties provide listeners with a greater challenge, and thus a greater stimulation to their imagination. Communication theorists suggest that, if people tend to interpret the world largely through their ability to see it, then being deprived of visual clues will compel them to supply such clues for themselves. Thus, when listening to a radio play, one needs to imagine not only a character’s thoughts but also that person’s appearance and surroundings. Radio dramatists argue that this offers greater intellectual and emotional reward to a listener—as opposed to a viewer—and allows the writer to create stories and characters that are truly experimental or fantastical, and that the medium of television would have to struggle to recreate visually for the viewer.

This appeal to the imagination is not confined of radio drama, since listeners of radio news and current-affairs or talk shows also have to create their own mental images of the people speaking and their physical surroundings. Programme-makers of all types will often concentrate, therefore, on portraying the sound of a person, a place, or an action as much as possible, in a way that prompts the listener to fill in the gaps accurately. Since each individual listener will create a different mental image, radio is also often described as an “intimate” medium: the ability to create a unique picture of a person speaking on the radio allows the listener to form a close relationship with that speaker as imagined, rather than as someone pre-realized on the listener’s behalf.

A

2

Intimacy and Convenience

This sense of intimacy is encouraged by the way most people listen to the radio. Television watching is often communal: families or small groups of people gather in the same room to watch a programme; most people listen to the radio alone. Presenters on the radio therefore tend to enhance the sense of intimacy by addressing the listener individually: a disc jockey will talk to “you” in the singular rather than “you” in the plural. Listeners feel that they are being talked to personally rather than being talked at as part of a large undifferentiated mass, and they respond by forming close attachments to individual presenters.

Since receiving sets are also highly portable, it is also easier to do something else while listening to the radio, whether it be housework, factory- or office-work, jogging, or driving a car. It is thus often described as a “secondary” medium. Television sets can be portable, but most of what a TV programme is trying to say is lost if viewers do not actually look at the screen. The radio, however, is often on in the background, without any loss in utility. Radio is therefore assimilated into a listener’s daily life much more than are the other media: it reaches the listener when he or she is alone, in private, and while doing almost anything in almost any place.

Some of these characteristics of radio present difficulties when identifying listening habits. While it might now be easier than ever before to listen to the radio wherever a person is in the world, there is no guarantee that the listener is fully attentive. In Britain the BBC’s own audience research has drawn a distinction between those who stress radio’s “predominant role—as a source of entertainment” and those who stress its “subordinate role—as an accompaniment to other activities”. The former category of listeners might search for radio that challenges the intellect and perhaps even aspires to be an art form on its own merits; the latter might demand of the medium what has been described as “acoustic wallpaper”—that is, an undemanding background noise.

Audience attitudes suggest that a whole range of listening habits is likely, depending not just on a listener’s personal tastes or even the time of day, but also on the type of programme being broadcast. Even so, the growth in the number of push-button receivers, as distinct from older sets requiring manual retuning, has increased the “promiscuity” of listeners during the 1980s and 1990s: they can—and do—change stations if they do not like what they hear. If rival broadcasters wish to protect advertising revenue by retaining their market share of listeners, the economic imperative often leads programming in the direction of ever more unchallenging—and therefore unobtrusive—output.