Тексты для изучающего чтения, перевода и закрепления грамматики
Text 2(A) Fundamentals of Radio
Radio transmission and reception was perhaps one of the earliest applications of electronics, the application that made the greatest impact on society. Surprisingly enough, we can use radio, predict its properties and design circuits that work very efficiently, but we know little about the real nature of radio. Ask an electronic engineer what radio is, and the answer will be a confident “electromagnetic waves"” Ask a physicist what electromagnetic waves are, and he will tell you that really we do not know.
We do know that electromagnetic radiation is a form of energy, and that it is propagated as waves. The model became more of a model and less like reality when we discover that radio travels through vacuum. One has to understand how can there be waves in a vacuum. Perhaps in the future, theoretical physics will give us an answer.
Possibly the hardest concept to understand radio is the way in which circuits can broadcast or communicate radio waves.
As to communication it is a process of conveying intelligence from one point to another by radio.
At the start, and also at the end of the communication process radio technique is identical with that of wire telephony and telegraphy. Radio differs from other methods of communication in the means used to connect the transmitting and receiving points.
As we have already mentioned that the science of radio is centered round electromagnetic fields or waves. In fact, the term “radio” has been driven from “radiation” – the process of propagating or sending the waves into space.
The basic elements of any system of radio communication are: a transmitter and a receiver, a transmitting and a receiving antenna, a modulator, a cathode-ray tube, a relay, headphones, a loudspeaker, etc.
Text 2 (B) Radio Waves
Radio waves are electromagnetic waves used for radio-communication. According to their frequencies electromagnetic waves produce different effects and are generated and detected by different methods. The waves of highest frequency so far discovered are cosmic rays, which appear in interstellar space and reach the earth from all directions. Next in order down the frequency spectrum come X-rays, ultra-violet rays and ordinary light space, to be followed by infrared rays and radio waves. The frequencies of radio waves are too low to be perceived¹ by the eye, although they are of exactly the same type as light waves, which operate on higher frequencies. Because of their low frequency, radio waves have to be collected on an aerial system and made perceptible by converting them to sound or vision. They have a great advantage over other forms of communication in that they follow the curvatures² of the earth and so are suitable³ for communication over great distances.
NOTES: ¹ to perceive – воспринимать; ² curvature –искривление; ³ suitable –подходящий, соответствующий
Text 2 (C) Basic Receivers and Transmitters
A much simplified transmitter block-diagram is shown in Fig. 1. This could be called the all-purpose block-diagram since it could be easily converted to a low-level or high-level amplitude modulation transmitter, a single sideband transmitter, or a frequency modulation transmitter. Obviously in the example, the circuit details would vary greatly, particularly in the modulators, and if detailed block diagrams were drawn the underlying similarities in structure would be less obvious.
ARIAL
 | |||||||||
 | |||||||||
|
| ||||||||
 |
The basic туре of a receiver is a tuned radio frequency, however, this is rarely used. The standard receiver configuration is the superheterodyne (superhet) shown in Fig.2.
| |||||||||||||||
 |  |
| |
| |||||||||||
 | |||||||||||||||
|
Fig.2. Basic superheterodyne receiver block-diagram
The desired radio frequency (r.f.) is converted to a constant intermediate frequency by taking the difference frequency after mixing the received signal with the output from a local oscillator. Since most of the amplification and selectivity is provided by constant frequency and bandwidth stages, the design problem is eased.
In both the transmitter and the receiver, r.f. oscillators have to be tuned to different frequencies. In the transmitter it is the master oscillator, while in the receiver it is the local oscillator. Modern practice is to use a frequency synthesizer with a single crystal to provide stability and accuracy.
Text 2 (D) Current and Future Developments of Radio Systems
Changes in aircraft radio systems occur more and more frequently. The first airborne radio equipment¹ used thermionic devices², cat’s whisker detectors³ and large parallel plate tuning capacitors4; power, weight and size were restrictions on the development of such equipment. In the 1950s transistorized equipment began to appear although not completely transistorized. Even now thermionic devices are still with us in the shape of the magnetron and the cathode-ray tube. Claims concerning all solid-state weather radars were made about mid-1979, and commercially available equipment appeared in 1980. The cathode-ray tube will remain with us for many years but will eventually be replaced by a matrix of electroluminescent elements.
Transistorized equipment is, of course, still marketed, but many of the transistors, diodes and resistors now appear on integrated circuits. The emergence of integrated circuits has revolutionized the design of air radio systems. The use of IC techniques to produce microprocessors has opened up a new world. Increased safety, increased payload, increased reliability and improvement in performance allow flights to be made in conditions where previously aircraft have to be grounded. Completely new systems do not appear very frequently, although when they do, it is often because the improvement in the state of the art made the impossible possible.
NOTES: ¹airborne radio systems – бортовое радиооборудование; ²thermionic devices - термоэлектронные устройства; ³cat’s whisker detectors – детекторы (датчики) с нитевидным кристаллом; parallel plate tuning capacitors – конденсатор настройки с параллельными анодами
Контрольная работа № 2
Вариант 1
1. Перепишите предложения; подчеркните в каждом глагол-сказуемое и определите его видо-временную форму и залог. Переведите предложения на русский язык. В разделе (Б) обратите внимание на особенности перевода конструкций со страдательным залогом, в разделе (В) – на место предлога в русском языке.
Образец: were agreed upon – Past Ind. (Simple)Passive от глагола to agree
(A) 1.While engineers were testing a new high-frequency device the power supply was suddenly interrupted. 2.A number of investigations has shown that the poles of the Earth’s magnetic field have reversed many times. 3.When the user gets into trouble, he can discover by reading the instruction book what he is doing wrong. 4.Russian astronomers have concluded that the Earth is hit by cosmic bodies as often as the Moon. 5.A new welding machine will be put into operation next week.
(Б) 1.A subroutine may be used many times during the computation of a programme but is written only once in the whole programme. 2.A computer must be told what operation to perform by means of instructions. 3.The students were shown a flow chart, which was very helpful for understanding interrelationship between various parts of a code. 4.We hope that during the discussion we’ll be offered some new ways of solving this problem. 5.He was promised immediate help.
(B) 1.No special attention was paid to the early period of this scientist’s activity. 2.His remark wasn’t taken notice of. 3.He would like to read the article referred to by the professor. 4.The decision insisted upon could not be accepted. 5.The lecture was followed by a discussion.
2. Заполните пустые графы таблицы номерами соответствующих предложений:
| Время | Характеристика действия (вид) | ||
| Простое (неопределенное) | Длительное (продолженное) | Завершенное | |
| Настоящее | 1, | ||
| Прошедшее | |||
| Будущее |
(А) 1.Я занимаюсь каждый день. 2.Я занимаюсь сейчас. 3.Я уже выучил уроки сегодня. 4.Я занимался английским вчера. 5.Я занимался английским, когда он пришел. 6.Я уже выучил первый урок, прежде чем начал второй. 7.Завтра я буду заниматься. 8.Я буду заниматься, когда вы придете. 9.Я уже выучу первый урок, перед тем как начну изучать второй.
(Б) 10.I was studying when they came. 11.I shall (I’ll) have studied Lesson Six when I start Lesson Seven. 12.I have already studied Lesson One.13.I study every day. 14.I shall be studying when you come. 15.I am studying now. 16.I studied yesterday. 17.I shall study tomorrow. 18.I had studied Lesson One before I began to study Lesson Two.
3. Определите, какой английской форме глагола соответствует данный русский перевод (например, 1г, 2д и т.д.):
1. write а) пишу (сейчас)
2. am writing б) писал (вчера)
3. have written в) напишу (завтра)
4. wrote г) написал (уже)
5. was writing д) буду писать (когда ты придешь)
6. will write е) пишу (регулярно)
7. will be writing ж) писал (когда ты пришел)
4. Перепишите и переведите предложения. Поставьте их в отрицательную форму. Задайте общий и специальный вопросы к каждому предложению.
1.She is having an English lesson now. (What lesson?) 2.They are translating a very interesting article. (What?) 3.She is listening to the news. (Who?) 4.I have just received a letter from my friend. (From whom?) 5.He has already been to London for three times. (How many times?) 6.She has just gone to the lecture. (Where?) 7.My mother was reading a book all the evening yesterday. (At what time?) 8.I was writing a report at this time yesterday. (Who?) 9.The doctor was examining the patients at 10 o’clock in the morning. (Whom?)