I. Read and translated the text

Noise

Noise is a serious problem for radio communication practically of any kind. There exist different types of noise. Each type has its cause and, therefore, has been given its name.

Among different types of noise there is hum, a steady low-frequency note, produced when the frequency of the alternating-current power supply becomes impressed onto the signal. The usual cause of hum is poor filtering.

Hiss and whistle, steady high-frequency notes, are produced by audio-frequencies oscillations, or by beats. Naturally, these noises cause disturbances and, therefore, they should be minimized and, in the end, eliminated.

The elimination of noises depends, first of all, on the design and construction of the receiver. It should be noted, however, that there exist types of noise that cannot be eliminated. The most important of these are statics — noises caused by electrical disturbances in the atmosphere.

To the causes of statics also belong disturbances caused by the opera-lion of nearby electrical equipment, such as, for example, automobiles.

II. Master the following words.

to impress внедрять, печатать

to disturb беспокоить, создавать помехи

hum гудение, гул

hiss шипение

whistle свист

statics атмосферные помехи

steady устойчивый, постоянный

poor слабый, бедный

Therefore поэтому, следовательно

III. Read the text

Radar

Radar is classified as means belonging to the sphere of radio communication. The word RADAR is an abbreviation of the words Radio Detection And Ranging. Radar as a term is now used to include any system employing microwaves.

To them belong microwaves ranging from 30 cm to 1 mm. Radar as a system of communication is used for locating, identifying, or guiding such moving objects as ships, aircraft, missiles, or artificial satellites. The radar system consists essentially of a generator, of electromagnetic radiation, the output of which is pulse modulated.

Then the output is fed to a movable aerial where from it is radiated as a beam. The aerial is rotating continuously when in use. The basic principle of radar is the scanning of the area by a beam of microwaves and detection of the waves that arc reflected from the object to be located.

The time taken for a pulse to travel to the object and back can be measured. In this way the distance to the object from the transmitter can be calculated, and its direction can be defined from the detection of the aerial direction. This technique has been extended to the use of computers, which accept data, apply logical processes to the data and supply the results of these processes as the information being sought.

IV. Answer the questions

1. What is the basic principle of radar?

2. What is radar as a system of communication used for?

3. What function does a movable aerial perform?

4. What device was the radar technique extended to?

5. How is modulation defined?

6. What is the meaning of the abbreviation "radar"?

7. What kind of waves does radar employ?

V. Read and translate the text

What is the radar for?

Radar is a system that uses radio waves to detect, determine the distance or speed, objects such as aircraft, ships, rain and map them. Speed detection is measured by the amount of Doppler Effect frequency shift of the reflected signal. A transmitter emits radio waves, which are reflected by the target, and detected by a receiver, typically in the same location as the transmitter. Although the radio signal returned is usually very small, radio signals can easily be amplified, so radar can detect objects at ranges where other emission, such as sound or visible light, would be too weak to detect. Radar is used in many contexts, including meteorological detection of precipitation, air traffic control, police detection of speeding traffic, and by the military.

Several inventors, scientists, and engineers contributed to the development of radar. The use of radio waves to detect "the presence of distant metallic objects via radio waves" was first implemented in 1904 by Christian Hulsmeyer, who demonstrated the feasibility of detecting the presence of ships in dense fog and received a patent for radar as Reichspatent Nr. 165546. Another of the first working models was produced by Hungarian Zoltan Bay in 1936 at the Tungsram laboratory.

The term RADAR was coined in 1941 as an acronym for Radio Detection and Ranging. This acronym of American origin replaced the previously used British abbreviation RDF (Radio Direction Finding). The term has since entered the English language as a standard word, radar.

A radar system emits powerful pulses of radio waves and listens for any echoes. By analyzing the reflected signal, the reflector can be located and sometimes identified. Although radio waves can be easily generated at any desired strength, the amplitude of the signal returned is usually very small. However, radio signals can easily be detected and amplified many times, so radar is suited to detecting objects at very large ranges where other signals, such as sound or visible light, would be too weak to detect. Radio waves can propagate with less attenuation than light in many conditions, for example, through clouds, fog, or smoke, enabling detection and tracking in conditions that prevent the use of other means.

VI. Answer the questions:

1.What is the function of radar?

2.Where do people use radars?

3.Who contributed to the development of radar?

4.What is the meaning of the acronym radar?

5.What are the principles of working of radars?

VII. Match the words with their definitions.

1) propagate a) apparatus for receiving signals

2) transmitter b) create something new

3) radar c) a piece of equipment which emits

4) receiver radio waves d) electronic impulse in radio, TV, etc.

5) source e) a system that uses radio waves to