Unit V 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

• · ·
· • ·
· · •
• · · ·
· • · ·
· · • ·

EXERCISE 2

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

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.

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 5

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 6

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. At any rate – 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 - вот почему.

EXERCISE 7

Give definitions of the following terms:

1. amplifiers,

2. frequency converters,

3. transmitters,

4. receivers,

5. radio waves,

6. radar,

7. laser.

EXERCISE 8

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 9

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)____________________________________________.

EXERCISE 10

Read text “Navigation” with the dictionary. Ask and answer questions about the text with your partner

Navigation

All satellite navigation systems use satellites with precision clocks. The satellite transmits its position, and the time of the transmission. The receiver listens to four satellites, and can figure its position as being on a line that is tangent to a spherical shell around each satellite, determined by the *time-of-flight of the radio signals from the satellite. A computer in the receiver does the math.

Radio direction-finding is the oldest form of radio navigation. Before 1960 navigators used movable loop antennas to locate commercial AM stations near cities. In some cases they used marine radiolocation beacons, which share a range of frequencies just above AM radio with amateur radio operators. Loran systems also used **time-of-flight radio signals, but from radio stations on the ground. VOR (Very High Frequency Omnidirectional Range), systems (used by aircraft), have an antenna array that transmits two signals simultaneously. A directional signal rotates like a lighthouse at a fixed rate. When the directional signal is facing north, an omnidirectional signal pulses. By measuring the difference in phase of these two signals, an aircraft can determine its bearing or ***radial from the station, thus establishing a line of position. An aircraft can get readings from two VOR and locate its position at the intersection of the two radials, known as a "fix." When the VOR station is collocated with DME (Distance Measuring Equipment), the aircraft can determine its bearing and range from the station, thus providing a fix from only one ground station. Such stations are called VOR/DMEs. The military operates a similar system of navaids, called TACANs, which are often built into VOR stations. Such stations are called VORTACs. Because TACANs include distance measuring equipment, VOR/DME and VORTAC stations are identical in navigation potential to civil aircraft.

*time-of-flight – пролет времени

**radial - 1) радиальный; лучевой; лучеобразный

radial road — радиальная дорога,

radial axle — радиальная ось

***navaid - 1) аэронавигационное вспомогательное оборудование, 2) средства обеспечения судовождения;

2) лучевой

EXERCISE 11

Speak about amplifiers, their role in communication and branches of use