ĐIỆN tử VIỄN THÔNG DTVT2 nhom4 bai6 txt khotailieu

Short wavelength Long wavelength Low frequency High frequency Visible light Task 2: Reading Information transfer Proagation of radio waves Radio waves from a transmitting aerial can tra

Radio D8-DTVT2

Group 4 :

Ngô Đắc Quân

Lê Văn Hoạch

Phùng Thế Quảng

Phạm Thị Minh Phượng

Nguyễn Thị Phương

Nguyễn Nhật Thư

Nguyễn Tuấn Anh

Task 1: Turning in

Study this diagram Name five things, other than radio which make use of electromagnetic waves.

Short wavelength

Long wavelength

Low frequency

High frequency

Visible light

Task 2: Reading Information transfer

Proagation of radio waves

Radio waves from a transmitting aerial can travel in one or more of three different ways

Surface or ground wave

This travels along the ground, following the curvature of the earth’s surface Its range is limited mainly by the extent to which energy is absorbed from it by the ground Poor conductors, such as sand, absorb more strongly than water, and the higher the frequency the greater the absorption The range is about 1500km at low frequencies (long waves)

Table 1

Surface wave

Task 3: Work in pairs

Sky wave

It travels skywards and, if it is below a certain critical frequency (typically

300MHz), is returned to earth by the ionosphere This consists of layers of air molecules stretching from about 80km above the earth to 500km On striking the earth, the sky wave bounces back to the ionosphere where it is again gradually refracted and returned earthwards as it by ‘reflection’ This continues until it is completely attenuated

The critical frequency varies with the time of day and the seasons Sky waves of high frequencies can travel thousands of kilometres but at VHF and above the usually pass through the ionosphere into outer space

Space wave

For VHF, UHF, and microwave signals, only the space wave, giving line of sight transmission, is effective A range of up to 150km is possible on earth if the

transmitting aerial is on high ground and there are on intervening obstacles such

as hills, buildings, or trees Space waves are aslo used for satellite

communications

Travels Skywards and returned to

earth by the ionosphere

line of sight transmission

Difficulties attenuated by refraction hills, buildings, or trees

Task 4: With the help of Table 1 and 2, label the diagram using these labels:

1-a transmitting aerial

2-e surface wave

3-d space wave

4-c sky wave

5-b receiving aerial

Task 5: Link these pairs of actions Use short ways when this is possible

1, When the switch is closed, current flows through the primary of the

Transformer

2, On striking, The radar signal is reflected

3, When discharging quickly, A cell may become hot

4, On receiving signals from the remote control, the TV follows your instructions.

5, On receiving the reflected signal, the signal is compared with the transmitted

signal

6,When choosing a course in electronics, you think carefully about your future.

7, On striking a high building, microwave signals are deflected.

8, When making a recording, you should ensure the recording levels are

satisfactory

9, On detecting an intruder, the alarm triggers an audible warning.

10,On pressing remote control button, the television set changes channel.

Task 6: Speaking practice

Task 7: Word study Word formation

Attenuate Attenuator Attenuation

Communicate Communicator Communucation

Induct Inductor Induction

Task 9: Technical Reading

1 : AF audio frequency

2 : RF Radio frequency

3 : AM Amplitude modulated

4: FM Frequency modulated

Task 10: Identify the waves Use these terms:

a : RF carier

b: AF signal

c: AM carrier

d: FM carrier

Task 11: Explain what happens at each stage in this flowchart,

which shows how a radio works The first and last stage are done for you.

Aerial Receiver weak RF signals

RF tuner Modulater Rf carrier

RF amplifier Amplifier RF wave

AF amplifier Amplifier AF signal

Loudspeaker Convert the audio signal into sound

Task 12:.

Radio waves are very popular in today's life It was used extensively in the field of communication today Here are all described block diagram of a simple radio receiver

Diagram includes seven components Aerial is receiving antenna, receiver RF carrier is modulated and put into an amplifier Audio signal is separated from the carrier and into the audio signal amplifier and power amplifier signal audio signal after amplification was converted and emitted speakers