Radio D8-DTVT2 Group : 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 Frequencies Travels Range Difficulties Task 3: Work in pairs Surface wave Low Frequency Along the ground 1500 km Absorption by the ground 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 Frequencies Travels Range Difficulties Sky wave Space wave below 300MHz Skywards and returned to earth by the ionosphere VHF, UHF Thousans km attenuated by refraction line of sight transmission 150km hills, buildings, or trees Task 4: With the help of Table 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 Verb Noun (component) Noun (property) Absorb Attenuate Communicate Conduct Absorption Attenuation Communucation Conductivity Absorber Attenuator Communicator Conductor Induct Modulate Reflect Resist Inductor Modulator Reflector Resistor Induction Modulation Reflection Resistance Task 9: Technical Reading : AF audio frequency : RF Radio frequency : 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 Component Function Aerial Receiver weak RF signals RF tuner Modulater Rf carrier RF amplifier Amplifier RF wave Detector Detect RF signal 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