Radio waves in the ionosphere

1. When a radio wave leaves a transmitting antenna, it travels in all directions. 2. One part of the signal travels along the ground and is called the ground wave. 3. The second part of the signal travels through the lower atmosphere in a direction parallel to the ground. 4. Another part travels at an angle to the ground. 5. The part travelling through the lower atmo­sphere is called the tropospheric wave; the part travelling at an angle to the ground — the ionospheric wave.

6. In the high-frequency part of the radio spectrum — 3—30 megacycles (mc) — the ground and tropospheric wave compo­nents travel short distances, not more than 25 or 30 miles. 7. The ionospheric wave component of the signal can travel to great distances, making long-distance short-wave communication possible.

8. While leaving the transmitting antenna, the ionospheric wave starts travelling and reaches a region called the iono­sphere. 9. This region begins at a height of about 60 miles above the ground. 10. On reaching the ionosphere, radio waves supply the free electrons of the region with electromagnetic energy. 11. As a result, the free electrons start vibrating and radiate this energy.

12. The ionosphere is formed primarily by ultraviolet radia­tion reaching it from the Sun. 13. As this radiation interacts with the gases in the upper atmosphere, these gases, which con­sist mainly of neutral molecules, absorb the ultraviolet energy, and in the process lose an electron. 14. This process leaves free electrons and positively charged gas molecules, which are called ions. 15. The formation of ions is called ionization.

16. The ionosphere has the property of bending radio waves and returning them to the ground at considerable distances from the point of transmission. 17. Bending may change the direction of the wave and it is returned to the ground at some distant point.

18. The ionosphere is not a single¹ region; it consists of several layers and the properties of these layers vary, depend­ing on many factors. 19. One of the layers, the F-layer², is of primary importance. 20. Most of the world's long-distance high-frequency communication takes place by means of reflec­tion of radio waves from this region. 21. The F-layer is at the height of about 175 miles.

22. Radio signals from the F-layer may be returned to the ground at distances as great as 2,000 miles from the transmitter.

Пояснения к тексту

1. single — зд сплошной

2. the F-layer — слой F ионосферы

Слова для запоминания

п height [hait], layer

и bend (bent), interact, lose (lost), supply

a distant, low, upper

ado mainly.

Слова для повторения

п angle, direction, frequency, property, region

v change, consist, depend, leave (left), reach, take place, travel

a main

prep along, through .

УПРАЖНЕНИЯ

III. Прочтите предложения, определив функцию ''-ing"-формы, и переведите предложения:

1. Leaving a transmitting antenna, a radio wave travels in all directions.

2. Part of the signal travelling along the ground is called the ground wave.

3. The ionosphere has the property of bending radio waves and returning them to the ground.

4. Bending radio waves changes the directionof thewave.

5. Obtaining new data on the waves travelling was necessary for future investigations.

6. Without using superconducting materials it was impos­sible to perfect this system operation.

7. Building a network of transmitting stations in that re­gion was of prime importance.

8. The transmitter operating on low frequencies was construc­ted by these students.

9. The scientists' main task was studying ionospheric condi­tions.

10. Constructing simple radio-sets was followed by more complex devices using semiconductors.

11. After finishing the experiment scientists started discussing its results.

IV. Прочтите и переведите предложения, обращая внимание способы перевода причастия I в форме страдательного залога:

1. Being heated magnetized steel loses its magnetism.

2. The new measuring instrument being developed in this laboratory will be tested by that engineer.

3. The oscillations being produced in the antenna are weak.

4. New data being obtained are necessary for future investi­gations.

5. Being perfected the device operated successfully under all conditions.

6. The new receiver being tested will be used in this system.

7. Being equipped with modern instruments the laboratory carried out important experiments.

V. Прочтите и переведите предложения, обращая внимание на перевод степеней сравнения имен прилагательных:

1. The more the weight the object has, the more work we must do in order to lift it.

2. The greater the number offree electronsin any metal,the greater is its conductivity.

3. The greater the distancebetween the plates, the less isthe capacity of a capacitor.

4. The lower the resistanceof the material, the more currentcan pass through it.

5. The higher the resistance of an insulator, the greater the applied voltage must be.

6. The higher we go into the atmosphere, the less is its pressure.

7. The larger the size of the electrodes, the more current capacity they can supply.

8. The higher the temperature, the quickeris the reaction.

VI. * Укажите дробью антонимы: к каждому слову из левой колонки (числитель) подберите его антоним из правой (знаменатель):

1. low 2. to lose 3. distant 4. a charge 5. to transmit 6. short 7. to absorb 8. to increase 9. possible 10. powerful

1. impossible 2. to receive 3. long 4. close [s] 5. to find 6. high 7. powerless 8. to decrease 9. to radiate 10. a discharge

VII. Прочтите и переведите сочетания слов:

1. at a great height; 2. at the height of 3 miles; 3. a thick layer; 4. a thin semiconductor layer; 5. to bend at right angle; 6. waves bending in the ionosphere; 7. to lose weight; 8. to lose electrons; 9. to supply considerable energy; 10. to supply modern equipment; 11. at low pressure; 12. at low frequency; 13. in the surrounding medium; 14. medium radio waves; 15. the main quality of the semiconductor; 16. to leave the atmosphere; 17. to leave the ground; 18. to change the direction of travel; 19. to move in upper layers of the atmosphere; 20. to consist mainly of neutral molecules

VIII. Прочтите и переведите предложения:

1. While improving the operation of the system, engineers used low weight equipment.

2. As a result, free electrons start vibrating and radiate much energy.

3. Measuring the temperature at various points was followed by studying its differences.

4. The first buildings housing the research laboratories have been constructed.

5. The ionosphere property of bending radio waves and re­turning them to the ground at considerable distances from the point of transmission was referred to in that text-book.

6. The properties of the ionosphere consisting of several layers depend upon many factors.

7. Electrons being negative move from lower to higher po­tential, that is from more negative to less negative.

8. Pressure is a very important parameter in investigating the atmosphere conditions.

9. The main task was supplying powerful energy sources for an orbital station.

10. The application of powerful relays resulting in better communication was the main subject of the discussion.

IX. Переведите, не пользуясь словарем:

Conductors

Conductors are materials having a low resistance, so that current easily passes through them. The lower the resistance of the material, the more current can pass through it.

The most common conductors are metals, and silverandcopper are the best of them. The advantage of copper is that it is much cheaper than silver. Thus, copper is widely used to produce wire conductors. One of the common functions of wire conductors is connecting voltage source to a load¹ resistance. Since copper wire conductors have a very low resistance a minimum voltage drop² is produced in them. Thus, all of the applied voltage can produce current in the load resistance.

Most materials change the value of resistance when their temperature changes.

Metals increase their resistance when the temperature increases while carbon decreases its resistance when the temperature increases. Thus, metals have a positive temperature coefficient of resistance while carbon has a negative temperature coefficient. The smaller is the temperature coefficient or the less the change of resistance with the change of temperature, the more perfect is the resistance material.

Пояснения к тексту

1. load—нагрузка

2. a drop — падение

X. Переведите, пользуясь словарем: