Vocabulary

Theme I: AIRCRAFT RADIO EQUIPMENT

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What Is Radio

Technically, radio is a small part of the electromagnetic spectrum so-called because electromagnetic waves are driven across space at the speed of light by electric and magnetic forces. Gamma rays, x-rays, ultra-violet, visible light and infra-red are also parts of the same spectrum. They all travel at the identical speed but have different properties and uses, depending on their frequency or wavelength _____If equipment generating radio frequency energy (a transmitter) is connected to an antenna (or aerial) the energy is radiated in the form of radio waves. Some of the radiated energy can then be collected by another antenna which, when coupled to a radio receiver, enables a link to be made between the transmitter and receiver. Adding information to the radio carrier wave enables messages to be transmitted. These messages may take the form of television programmes, voice messages, data or other forms of radio communication. Radio is an immensely versatile medium. _____The way in which radio waves propagate or travel through the atmosphere varies with the frequency or wavelength of the radio signal. In general, the lower the frequency the further the distance that radio waves will travel. As the frequency increases, the waves may be obstructed or deflected by hills and buildings. At extremely high frequencies, rainfall and other weather conditions can significantly limit the effective operating range of radio communications. These propagation characteristics mean that different bands of frequencies are suited to particular types of radio use. For example, for national and international broadcasting the long-wave (approximately 148-283 kHz) and medium-wave (approximately 526-1606 kHz) bands are used. At the higher frequencies such as VHF (Very High Frequency - 30 to 300 MHz) and UHF (Ultra High Frequency - 300 to 3000 MHz), where the effective transmission range is shorter, the bands are more suited to local broadcasting or local coverage for mobile radio systems. At higher frequencies it is possible to allocate wider channels (i.e., more bandwidth) and this allows more information to be transmitted per channel than at lower frequencies. For example, at VHF, because of the greater bandwidth available, high quality stereo music can be transmitted, but a typical channel in the long wave bands will support only a low quality music broadcast.

Vocabulary

electromagnetic spectrum - электромагнитный спектр electromagnetic waves - электромагнитные волны frequency - частота versatile medium - многоцелевое средство propagate - распростроняться obstruct - препятствовать broadcast - передавать по радио, вещать significantly - значительно band - полоса частот range - дальность передачи deflect - отклоняться wavelength - длина волны coverage - зона действия, радиус слышимости allocate - размещать, распределять receiver - приёмник transmitter - передатчик

Answer

1. What is radio?

2. What are the parts of spectrum?

3. What equipment is necessary for radio communication?

4. What does the wave propagation depend on?

5. What are Very High Frequency (VHF) and UHF more suited to?

6. What are long-wave and medium-wave used for?