3. Translate and memorize the following word-combinations.

Floor space, broadcast, short-wave transmission, carrier of frequency, constant pressure, position of rest, undamped current, natural frequency, tuning fork, harmonic vibration.

4. Match English words and word-combinations with their Ukrainian equivalents.

1. 2. 3. 4. 5. 6.7. 8. 9. 10

Metal panel Mounted Ground potential Accessible Minimize Stationary Inductance Alternator Transmitted Desired result

a. b. c. d. e. f. g. h. i. j.

Переданий Доступний Металевий приборний щит Встановлений на висоті Генератор змінного струму Бажаний результат Постійний, незмінний Базова напруга, потенціал Зменшувати Індуктивність

5. Choose the correct variant.

1. A radio transmitter is a device for … radio frequency energy.

1. consuming; c) producing;

2. processing; d) transforming.

2. Commercial transmitting equipment is … … a frame-work.

1. located under; c) based at;

2. balanced with; d) mounted on.

3. The … frame is normally enclosed with wire mesh.

1. plastic; c) iron;

2. metal; d) steel.

4. When the microphone is not spoken into the diaphragm remains … .

1. changeable; c) moving;

2. stationary; d) mobile.

5. In order to minimize the resulting interference it is essential that the carrier frequencies be as nearly … as possible.

1. opposite each other; c) the same;

2. different; d) negative.

6. When the diaphragm is displaced outwardly, the … takes place.

1. front; c) amplitude;

2. direct; d) reverse.

6. Answer the following questions.

1. What is a radio transmitter?

2. Where is transmitting equipment mounted on?

3. What radio transmitting equipment do you know?

4. How can radio transmitters be used?

5. How many elements does a microphone transmitter consist of? What are they?

6. Describe the behaviour of the diaphragm.

7. What happens to the diaphragm when the microphone is/is not spoken into?

8. When does the reverse take place?

7. Represent the scheme of a radio transmitter or a microphone transmitter. Describe the principles of their work.

8. Translate into English.

1. Радіопередавач – це пристрій для передачі радіочастотної енергії.

2. Складовими радіопередавача є випромінювачі, посилювачі напруги, безперебійні джерела енергії, модулятори та системи енергозабезпечення.

3. Більшість передавачів створені для короткохвильової трансляції.

4. Якщо в мікрофон не говорять, генератор змінної напруги виробляє високочастотний струм з постійною амплітудою.

5. Коли в мікрофон говорять, створюється певний тиск, який викликає коливання діафрагми.

TEXT B

1. Read and translate the text in a written form: Electromagnetic Waves

Radio waves, light, X-rays and some cosmic rays- they all belong to the same family. They travel at a velocity of light.

The wave has both electric and magnetic components which are bound together. At the end of its travel the wave gives up energy. The other waves are those we know as wireless waves.

Visible light covers a very small part of the electromagnetic spectrum. Just above and below the visible light range are ultraviolet and infrared light. The ‘ultra’ in ultraviolet tells us that this light lies at frequencies higher than that of violet light lies; and the term ‘infra’ in infrared tells us that this light lies at frequencies lower than red.

Ultraviolet has shorter, and infrared has longer wave lengths than visible light. The radiations were discovered long before anyone thought of electromagnetism. When light was passed through a prism and formed a spectrum on screen, scientists found that heating effect occur beyond the edges of the visible light spectrum.

Ultraviolet radiation produces many effects, some useful and some unpleasant. A certain amount of ultraviolet radiation is good for our health. It helps to form vitamin D in the skin which is important for the promotion of bone-growth. Ultraviolet light also kills microbes, and for that reason it is used in hospitals and to sterilize food. Ultraviolet rays are familiar to most people as the particular art of sunlight that is “heath-giving”. The use of these rays in diagnosis is a powerful weapon of medicine. One of the most valuable uses of ultraviolet rays in industry is testing of the quality of certain goods.

Direct ultraviolet radiation is very bad for the eyes. This is one reason why it is dangerous to look directly at the sun. On the other hand, the human eye is quite capable of dealing with normal doses of scattered ultraviolet light.

Infrared energy is being used in automatic regulation of chemical and biological processes, temperature measurement and control during manufacture of textiles, plastics and metals.

2. Make up a plan of the text in the form of questions.

TEXT C

1. Mind the following words:

1. indispensable – необхідний

2. ether – ефір

3. metallic welding – метало зварка

2. Listen to the text and try to understand it.

3. Answer the following questions:

1. Is infrared energy of a great importance for people?

2. When are waves ‘seen’ as ultraviolet?

3. What rays are shorter than ultraviolet?

4. How does the penetrative power of the waves change?

5. Where can X-rays be used?

UNIT 11

TEXT A

Receivers

1.Read and memorize the following words and word-combinations and their translations.

1. Radiation – джерело радіохвиль;

2. Separate – відділяти;

3. Carrier – носій;

4. Detection – детектування;

5. Aerial – антена;

6. Modulate – занижувати частоту;

7. Rectification – вирівнювання;

8. Grid – сітка, мережа;

9. Valve – електролампа;

10. Biased – зі скосом;

11. Swing – коливання;

12. Emergent – те, що раптово виникає;

13. Rectifier – вирівнювач.

2.Read and translate the following text.

A radio receiver has two main functions to perform: firstly, it has to select the required radiation from all the other electromagnetic waves that are present over the surface of the Earth, and secondly, it has to separate (or demodulate) the radio-frequency current from the radio-frequency carrier. This process is also called detection.

The selection is effected by making use of a resonant circuit. If a resonant circuit in the receiver is tuned so that it will oscillate at the same frequency as the carrier-wave that is to be received, it is clear that of all the electromagnetic waves picked up by the receiving aerial, the only one that will be selectively strengthened will be the one with a frequency exactly fitting the resonance of the tuned circuit. This aspect of resonance is familiar in connection with sound waves if a note is played on the piano in a room containing a glass tumbler with a natural resonant frequency the same as that of the note, then the glass will vibrate in resonance with the note, and may even shatter.

The receiving aerial, then, collects the modulated carrier-wave and feeds it into a circuit tuned to resonate at the frequency of the carrier-wave. This tuning can be effected by altering the capacitance of the capacitor of the resonant circuit.

The second function of a receiver is to demodulate the carrier-wave; again this operation can be performed by using an electronic valve. Valves are not only used for amplification, they also serve another purpose-rectification, that is to say, they will only permit current to flow in one direction. Thus, if a modulated carrier-wave is fed into the grid of a triode valve, and the grid is correctly biased, only current flowing in one direction will pass through the valve, the bottom half, or negative swing, of the wave be cut off.

The shape traced by the peaks of the emergent half of the carrier-waves is the same as the original audio-frequency current, so that if these half-waves are fed into the earphones or at loudspeaker, the original sound wave will be reproduced. The half-waves of the carrier themselves will not, of course, affect the earphones or loudspeaker, as their frequency is far too high. Demodulation has therefore been achieved by the use of an electronic valve as a rectifier.

Rectification can also be brought about by the use of certain crystals, which have the property of allowing current to pass in one direction only. These crystals were used in the early days of radio in crystal sets; transistors and the semiconductor diode are a more modern application of the same principle.