Text III Radio and Television

EXERCISE 1

Read and translate the text.

Radios transmit and receive communications at various preset frequencies. Radio waves carry the signals heard on AM and FM radio, as well as the signals seen on a television set receiving broadcasts from an antenna. Radio is used mostly as a public medium, sending commercial broadcasts from a transmitter to anyone with a radio receiver within its range, so it is known as a point-to-multipoint medium. However, radio can also be used for private point-to-point transmissions. Two-way radios, cordless telephones, and cellular radiotelephones are common examples of transceivers, which are devices that can both transmit and receive point-to-point messages.

Personal radio communication is generally limited to short distances (usually a few kilometers), but powerful transmitters can send broadcast radio signals hundreds of kilometers. Shortwave radio, popular with amateur radio enthusiasts, uses a range of radio frequencies that are able to bounce off the ionosphere. This electrically charged layer of the atmosphere reflects certain frequencies of radio waves, such as shortwave frequencies, while allowing higher-frequency waves, such as microwaves, to pass through it. Amateur radio operators use the ionosphere to bounce their radio signals to other radio operators thousands of kilometers away.

EXERCISE 2

Look through the words below and practice in pronunciation. Learn them by heart.

preset - заранееустанавливать, задавать

range – диапазон

two-way radio - приёмно-передающаярадиоустановка

cellularradiotelephone - сотовая радиотелефонная связь

transceiver - приемопередатчик, радиопередатчик и радиоприемник в общем корпусе

amateurradioenthusiasts - радиолюбители

bounceoff - отскакивать рикошетом от чего-л.

EXERCISE 3

Retell the information using the words from the vocabulary.

EXERCISE 4

Match the following phrases with their meanings:

very high frequency (VHF) ultrahigh frequency (UHF) terrestrial link unscramble satellite dish high-resolution picture aspect ratio width

форматное соотношение спутниковая антенна ширина изображение высокого разрешения наземная линия связи ультравысокая частота, УВЧ (300 - 3000 МГц) расшифровывать очень высокая частота, ОВЧ (30-300 МГц)

EXERCISE 5

Read and translate the text. Make up the questions to the information of the text.

Television is primarily a public broadcasting medium, using point-to-multipoint technology that is broadcast to any user within range of the transmitter. Televisions transmit news and information, as well as entertainment. Commercial television is broadcast over very high frequency (VHF) and ultrahigh frequency (UHF) radio waves and can be received by any television set within range of the transmitter. Televisions have also been used for point-to-point, two-way telecommunications. Teleconferencing, in which a television picture links two physically separated parties, is a convenient way for businesspeople to meet and communicate without the expense or inconvenience of travel. Video cameras on computers now allow personal computer users to teleconference over the Internet. Videophones, which use tiny video cameras and rely on satellite technology, can also send private or public television images and have been used in news reporting in remote locations.

EXERCISE 6

Read the text and underline the best word in each set.

Cable 1(television, radio, Internet) is a commercial service that links televisions to a source of many different types of video programming using coaxial cable. The cable provider 2(catches, obtains, acquires) coded, or scrambled, programming from a communications satellite, as well as from terrestrial links, including broadcast television stations. The signal may be scrambled to prevent 3(unchecked, uncoded, unpaid) access to the programming. The cable provider electronically unscrambles the signal and supplies the decoded signals by 4(air, signal, cable) to subscribers. Television 5(workers, users, makers) with personal satellite dishes can access satellite programming directly without a cable installation. Personal satellite dishes are also a subscriber service. Fees are paid to the network operator 6(in, out, to) return for access to the satellite channels.

EXERCISE 3

Read the text and try to say what kind of situation in the sphere of television in Russia is nowadays.

Most television sets outside of the United States that receive programming use different types of standards for receiving video signals. The European Phase Alternative Line standard generates a higher-resolution picture than the sets used in the United States, but these television sets are more expensive. Manufacturers now offer digital video and audio signal processing, which features even higher picture resolution and sound quality. The shape of the television screen is changing as well, reflecting the aspect ratio (ratio of image height to width) used for movie presentation.

UNIT V

FREQUENCY CONVERTERS

Text I

What are Frequency converters

EXERCISE EXERCISE EXERCISE EXERCISEEXERCISE 1EXERCISE EXERCISE

Before reading the text answer questions:

• What branch of technology are frequency converters connected to?

• What role do they play?

• In what devices are they used?

EXERCISE 2EXERCISE EXERCISE

Read and translate the international words:

Apparatus, system, channel, amplitude, modulation, unit, generators, electric filter, differential, limiter, compressors, correction, terminal, element, diode, transistor, transfer, spectrum, area, heterodyne, detector, receiver, conversion, process, principle of modulation, periodically, characteristics, radio, integrated, ordinary, balanced, crystal, professional, decameter, bipolar, unipolar, isolation, type.

EXERCISE 3

Find the Russian equivalents to the following words and word combinations in the box:

Multichannel system, frequency division of channels, amplitude modulation, a number of various devices, frequency converter, amplifier, differential system, amplitude limiter, electric filter, correction circuit, frequency spectrum, super heterodyne detector, intermediate frequency, diode, super high frequency, low noises, bipolar transistor, unipolar transistor, non-balanced converter, double balanced converter.

Амплитудная модуляция, многоканальная система, преобразователь частоты, ограничитель амплитуд, множество различных устройств, биполярный транзистор, полевой транзистор, частотное разделение каналов, усилитель, промежуточная частота, СВЧ, выравнивающий контур, спектр частот, супергетеродинный приемник, электрический фильтр, диод, дифференциальная система, малые шумы, двойной балансный преобразователь, небалансный преобразователь.

EXERCISE 4

Read and translate the text.

Apparatuses on multichannel and thin-route systems with frequency division of channels and amplitude modulation are comprised into a number of various devices commonly called units. Main units of a multichannel system with frequency division of channels and amplitude modulation are frequency converters, amplifiers, generators, electric filters and several special units – differential systems, transceiving devices, amplitude limiters, range extenders and range compressors, delineation circuits and correction circuits.

Frequency converters are one of the most important terminal units because they are the very devices to create multichannel systems with frequency division of channels and amplitude modulation. For this purpose in the converters there are used nonlinear elements: dead (semiconductor diodes) and active (transistors). There are also used frequency converters with electron tubes which help to obtain greater signal amplification.

Frequency converters are used to transfer frequency spectrum from one area into another. They are part of super heterodyne detector (a frequency converting receiver). The result of conversion is a new frequency value fcalled intermediate value. The intermediate frequency can be both higher and lower than signal frequency. In the first case the frequency conversion is upwards, in the other case it is downwards. In this process the frequency conversion principle of modulation is not broken, only fluctuation-carrier frequency is changed at the output of the converter.

To convert frequency there are used line circuits with periodically changing characteristics in radio receivers. The structural circuit consists of a converting element, heterodyne and filter. According to the type of a converting element the frequency converters are usually divided into diode, transistor and integrated converters. There is a different number of converting elements, so one can find the following types of converters: ordinary (with one converting element), balanced (two elements), and ring (4 elements).

Most SHF (super high frequency) receivers use crystal diodes as converting element. Crystals have fast response and comparatively low noises. But they have a drawback - they don’t have amplifying properties. Such converters are used in professional devices of decameter range.

Transistor converters use bipolar transistor, or unipolar transistor as converting element. Balanced converters are combination of two non-balanced converters. To increase channel isolation between a signal and a heterodyne there are used double balanced converters called ring converters. Such type converters have low noises and better amplitude characteristics. They are used in frequency range up to 100 MHz in professional decameter devices.

EXERCISE 5

Words and word combinations to be remembered:

Thin-routesystems – малоканальная система

unit – узел аппаратуры

transceivingdevices – устройство приема и передачи сигналов

rangeextenders – сжиматель диапазона

rangecompressors –ограничитель диапазона

delineationcircuits – выравнивающий контур

terminalunits – оконечная аппаратура

nonlinearelements - нелинейные элементы

dead – пассивный

semiconductor –полупроводник

amplification – усиление

frequencyspectrumtransfer – перенос спектра частот

upwards / downwards – вверх/ вниз

fluctuation-carrier frequency – частотанесущегоколебания

at the output of the converter – навыходепреобразователя

line circuits with periodically changing characteristics – линейныецеписпериодическименяющимисяпараметрами

integrated – интегральный

ordinary – простой

balanced -балансный

ring – кольцевой

unipolar –полевой

circuit isolation – развязкамеждуцепями

EXERCISE 6

Scan the text again and count how many times the words ‘converter’ and ‘amplitude modulation’ are used in different combinations. Also give 5 verbs, 5 adverbs and 5 nouns concerning the subject of the text. What verb is met in the text most often? In what voice?

EXERCISE 7

Answer the questions about the text:

1. What units can be called the main units of a multichannel system?

2. Which elements are used in frequency converters?

3. Which other elements, beside non-linear are enabled in communication apparatuses? What is their advantage?

4. Why do radio engineers need frequency converters?

5. What is changed with the help of the frequency converters?

6. What elements does the circuit of a FC (frequency converter) consist of?

7. What types of FC can you name?

EXERCISE 8

Fill in the gaps using proper words from the text.

1. Apparatuses on ______and thin-route systems with frequency division of channels and amplitude modulation are comprised into different_____.

2. Main units of a multichannel system are ______, amplifiers, generators, electric filters and several special units – differential systems, _______, amplitude limiters, range extenders and range compressors, _______ and correction circuits.

3. There are also used frequency converters with ______ which help to obtain greater signal amplification.

4. Frequency converters are used ______ frequency spectrum from one area into another.

5. In this process the frequency _______ is not broken, only _______ is changed at the output of the converter.

6. The structural circuit consists of a converting element, ______ and filter.

7. One can find the following types of converters: _____ (with one converting element), ______ (two elements), and _____ (4 elements).

8. Most SHF receivers use ______ as converting element.

9. Transistor converters use _____ transistor or ______ transistor as converting element.

EXERCISE 9

Translate sentences into Russian.

1.К основным узлам аппаратуры многоканальных систем с частотным разделением сигналов и амплитудной модуляцией относятся преобразователи частоты, усилители, генераторы, электрические фильтры.

2. Помимо основных узлов аппаратуры, существует ряд специальных узлов – дифференциальные системы, устройства передачи и приема сигналов, ограничители больших амплитуд, сжиматели и расширители диапазона, выравнивающие и корректирующие контуры.

3.Преобразователи частоты являются одним из важнейших узлов оконечной аппаратуры, поскольку только с их помощью возможно построение многоканальных систем с частотным разделением сигналов и амплитудной модуляцией.

4.При преобразовании частоты закон модуляции не нарушается, а изменяется только частота несущего колебания на выходе преобразователя.

5.В зависимости от вида преобразовательного элемента преобразователи частоты подразделяются на диодные, транзисторные, интегральные.

6.В зависимости от количества преобразовательных элементов выделяются следующие виды преобразователей: простые (один ПЭ), балансные (2 ПЭ), кольцевые (4 ПЭ).

7.Кристаллические диоды обладают малой инерционностью и сравнительно малыми шумами.

8.В транзисторных преобразователях частоты используют биполярный или полевой транзистор.