Text II am and fm broadcast radio

EXERCISE 1

Read and translate the text. Use the dictionary if you need.

AM broadcast radio sends music and voice in the Medium Frequency (MF—0.300 MHz to 3 MHz) radio spectrum. AM radio uses amplitude modulation, in which the amplitude of the transmitted signal is made proportional to the sound amplitude captured (transduced) by the microphone while the transmitted frequency remains unchanged. Transmissions are affected by static and interference because lightning and other sources of radio that are transmitting at the same frequency add their amplitudes to the original transmitted amplitude.

FM broadcast radio sends music and voice with higher fidelity than AM radio. In frequency modulation, amplitude variation at the microphone cause the transmitter frequency to fluctuate. Because the audio signal modulates the frequency and not the amplitude, an FM signal is not subject to static and interference in the same way as AM signals. FM is transmitted in the Very High Frequency (VHF—30 MHz to 300 MHz) radio spectrum. VHF radio waves act more like light, travelling in straight lines, hence the reception range is generally limited to about 50-100 miles. During unusual upper atmospheric conditions, FM signals are occasionally reflected back towards the Earth by the ionosphere, resulting in Long distance FM reception. FM receivers are subject to the capture effect, which causes the radio to only receive the strongest signal when multiple signals appear on the same frequency. FM receivers are relatively immune to lightning and spark interference.

FM subcarrier services are secondary signals transmitted "piggyback" along with the main program. Special receivers are required to utilize these services. Analog channels may contain alternative programming, such as reading services for the blind, background music or stereo sound signals. In some extremely crowded metropolitan areas, the subchannel program might be an alternate foreign language radio program for various ethnic groups. Subcarriers can also transmit digital data, such as station identification, the current song's name, web addresses, or stock quotes. In some countries, FM radios automatically retune themselves to the same channel in a different district by using sub-bands.

EXERCISE EXERCISE 2

Make up questions to the answers below

1.Q:______________________ ?

A: MF—0.300 MHz to 3 MHz

2.Q:__How ________amplitude and ________change?

A: The amplitude of the transmitted signal is made proportional to the sound amplitude captured (transduced) by the microphone while the transmitted frequency remains unchanged.

3.Q: What_________________affected ___?

A: Transmissions are affected by static and interference.

4.Q: ___________________________?

A: AM is transmitted in the Medium Frequency but FM is transmitted in the Very High Frequency

5.Q:____________________________?

A: 30 MHz to 300 MHz.

6. Q:___________________________?

A: to lightning and spark interference.

7.Q:___________________________?

A: They are secondary signals transmitted "piggyback" along with the main program.

EXERCISE 3

Work in pairs. Choose between the topics ‘AM broadcast radio’ and ‘FM broadcast radio’. Exchange information addressing to your partner, ask questions and get answers.

UNIT VI

AMPLIFIERS

Text I

What do we call Amplifiers

EXERCISE 1

Practice saying some words from this unit and put them in the right stress pattern box.

Terminal	Heterodyne	Demodulator	Fluctuation
apparatus	Relation	Therefore	Output
Intermediate	compression	Amplitude	Professional
frequency	controlling	transceiving	decameter

EXERCISE2

Work with the partner. Take it in turns to dictate abbreviations and write them down. Can you decode all of them?

IBM, IT, VHF, MHz, INMARSAT, UNIX, DOS, NT, OS, AM, FM, PC, NC, GPRS.

EXERCISE 3

Choose the word that doesn’t suit in each group

• Transformer, transistor, transabdominal, transfer, transceiver

• Radiation, fluctuation, modulation, meditation, acceleration

• Antenna, currant, radio wave, signal, Hertz

• Spectrum, apparatus, diagram, decameter, publicity

• Obsolete, modern, up-to-date, latest, experimental

• Converter, energizer, detector, amplifier, receiver, motor

• Trim, inclination, elevation, depression, deviation,

• Periodically, technically, visually, structurally, mechanically

• Focused, coherent, duplex, terminal, aperiodic

EXERCISE 4

Read the text and be ready to answer the questions after the text.

Amplifiers are essential units of terminal and intermediate apparatuses in multichannel systems. Amplifiers used in radio communication are divided into individual, generic and single-component signal amplifiers.

Individual amplifiers are designed to intensify signals in single channels. In modern multichannel systems which are built, as a rule on, the basis of generic principle, such amplifiers are used only in individual part of a terminal apparatus, amplifiers being installed after demodulator (a signal converter), therefore, they become amplifiers of sonic frequency. In multichannel systems created on the base of individual principle, individual amplifiers are used both in terminal and in intermediate apparatuses as means of intensification of high frequency current. Duplex amplifiers are individual too.

Generic amplifiers are used to intensify signals in channel banks. They are used both in batches of terminal apparatuses and in intermediate apparatuses of multichannel systems built on the base of batch principle. Both batch and individual amplifiers are used to intensify multichannel signals; hence, they should be aperiodic.

In addition to individual and batch amplifiers, in apparatuses of multichannel systems there are amplifiers which intensify the carrier current and currents of different controlling signals – pilot frequencies, telecontrol signals, and selection and calling signals. These signals are mostly fixed-frequency (sine) signals. Resonance amplifiers are used to intensify them.

Signal amplification can be provided either in frequency without its conversion or with conversion of frequency. Receiver intensifying radio frequency is called straight amplifier: receiver converting frequency in radiotrackt is called superheterodyne. Frequency amplifiers provide frequency intensification and its subsequent noise filtering.

Main electric properties of multichannel systems amplifiers are: gain factor or intensifying possibility of an amplifier and its frequency relation; input and output resistance of an amplifier; output power of an amplifier; gain compression appearing in amplifier; amplifier noises.

EXERCISE 5

Answer the questions.

1. What did you learn about amplifiers?

2. What types of amplifiers can you name?

3. What are individual amplifiers designed for?

4. Where are batch amplifiers used?

5. What other types of amplifiers, besides individual and batch amplifiers, can you name? How can we obtain signal amplification?

6. What are main electric properties of amplifiers?

EXERCISE 6

Find grammar mistakes in these sentences and correct them.

Amplifiers using in radio communication are divided into individual, generic and single-component signal amplifiers. - Amplifiers used in radio communication are divided into individual, generic and single-component signal amplifiers.

1. Modern multichannel systems which are built, as a rule on the basis of generic principle.

2. In multichannel systems created on the base of individual principle, individual amplifiers using both in terminal and in intermediate apparatuses.

3. Signal amplification can be providing either in frequency without its conversion or with conversion of frequency.

4. Resonance amplifiers used to intensify controlling signals.

EXERCISE 7

Here are some structuring your view expressions. Use each of them in sentences from the text “Amplifiers” where they logically fit.

E.g.: At any rate, amplifiers are essential units of terminal and intermediate apparatuses in multichannel systems.

1. Atanyrate – во всяком случае,

2. Consequently – следовательно,

3. hence, therefore – поэтому,

4. however – однако,

5. in fact, actually – фактически,

6. nevertheless – тем не менее,

7. moreover – более того,

8. that is why - вотпочему.

EXERCISE 8

Give definitions of the following terms:

1. amplifiers,

2. frequency converters,

3. transmitters,

4. receivers,

5. radio waves,

6. radar,

7. laser.

EXERCISE 9

Read and translate the dialogue.

A: The time is 1.05 and here is the business news with Alan Wilson.

B: Good afternoon. Share prices on the London stock market have fallen sharply today, following sharp losses on Wall Street. Shares of leading computer companies have been the worst hit. Lucy Lambert, Chief Analyst with Hancock and Benson, believes we are seeing the start of a sell-off in high technology shares.

C: Technology stocks have made enormous increases for some time. Now they are coming down to their correct level. That is just a short term correction. It’s not a repeat of the stock market crash of 1987.

B: The FT-SE 100 index closed 50.2 points down. British gas has reported a 4% drop in profits for the first half of the year. The company blames warm winters, a fall in gas prices and rising competition from rival suppliers. The Safeway supermarket chain has removed fifty-five thousand bottles of tonic water from their shelves after poison was discovered in four bottles. The police haven’t yet discovered where the poison was put there deliberately.

And finally, the human brain may be connected to computers within 50 years. Professor Peter Cochrane, the head of British Telcom’s Martlesham heath laboratories, has predicted connections between silicon chips and the human brain. By the year 2020 it may be possible for someone to carry a complete encyclopedia around in their head.

And that’s all from the business news studio today. We’ll be back tomorrow at five past one.

EXERCISE 10

Read the dialogue again to pick out specific information. Complete the sentences.

Item 1

(a)_________________________________ have fallen in London.

They also fell on (b)___________________________________.

The worst hit companies are (c)___________________________.

It’s not a repeat of the stock market crash of (d)____________________.

The FT-SE index closed (e)______________________points down.

Item 2

The company:

(f)__________________________________________________ .

The percentage fall in profits:

(g)______________________________________ .

Reasons for the fall:

(h) _____________________________________________ .

Item 3

The company: (i)_________________________________________________

Its problem:

(j) __________________________________________________ .

How it happened:

(k) ______________________________________________

Item 4

Who is professor Peter Cochrane? (l)__________________________________

What has he predicted?

(m) _________________________________________

When will it happen?

(n)____________________________________________.