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Section 3: Radio Communication

Section 3: Radio Communication . Radio Transmission The music and the words are sent to the radio by radio waves. The radio’s metal antenna detects the radio waves The electrons in the antenna vibrate and create a electric current

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Section 3: Radio Communication

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  1. Section 3: Radio Communication • Radio Transmission • The music and the words are sent to the radio by radio waves. • The radio’s metal antenna detects the radio waves • The electrons in the antenna vibrate and create a electric current • The information about the music and the words are sent to the speakers • The music and words are transferred to your ears

  2. Section 3:Radio Communication • Dividing the Radio Spectrum • Radio Stations are assigned a particular frequency. • Turning the dial of your radio changes frequencies. • The set frequency is called a carrier wave. • The radio station has to send information about the sounds that you are hearing. • The information is sent by modifying the carrier wave.

  3. Section 3:Radio Communication • AM Radio (Amplitude Modulation) • Radio Stations broadcasts information by varying amplitude of the carrier wave • Your radio detects these changes • The changing electric current makes the speaker vibrate • 540,000-1,600,000 Hz

  4. Section 3:Radio Communication • FM Radio (Frequency Modulation) • The frequency is varied to create FM waves. • The strength of the waves are fixed • FM tends to be more clear than AM • 88 million to 108 million Hz • The frequency is much stronger and more clear than AM

  5. Section 3:Radio Communication • Television • Television and radio transmitters are similar. • These signals are broadcasted by a carrier wave. • The audio of TV is broadcasted by FM waves • The color and brightness of the show is broadcasted by AM waves.

  6. Section 3:Radio Communication • Cathode-Ray Tubes • The CRT in a color TV produces three electron beams that are focused by a magnetic field and strike the screen. • The screen is specked with rectangular spots. • Red • Green • Blue • These spots are grouped with one of each

  7. Section 3:Radio Communication • Cathode-Ray Tubes (cont) • The image is created when the three electron beams of CRT sweep back and forth. • By varying the brightness of each spot in a group the spots form any color.

  8. Section 3:Radio Communication • Telephones • Until 1950, human operators were needed to connect many calls. • When you speak into a telephone: • A microphone converts sound waves into an electrical signal. • The waves are transmitted to and from a microwave tower. • It uses another signal for receiving information from the base station

  9. Section 3:Radio Communication • Telephones • The base stations are several kilometers apart. • The area each one covers is called a cell. • If you move from one cell to another the signal automatically switches.

  10. Section 3:Radio Communication • Cordless telephones • Like a cellular telephone a cordless phone is a transceiver. • Transceivers transmits one signal and can receive another. • You must be within range of the base unit • Many cordless phones have frequency buttons.

  11. Section 3:Radio Communication • Pagers • Allows messages to be sent to a small radio receiver. • A caller leaves a message at a terminal • At the terminal the message is changed into a signal. • The signal is transmitted to the pager after receiving a ID number. • Newer pagers can send data and also receive.

  12. Section 3:Radio Communication • Communications Satellites • Thousands of satellites have been launched into orbit. • A station broadcasts a high-frequency microwave signal to the satellite. • The satellite receives the signal, amplifies it and then transmits it to a certain area on the globe. • The frequencies are different than those on earth.

  13. Section 3:Radio Communication • Satellite Telephone Systems • IF you have a moble telephone, you can make a phone call when sailing across the ocean. • The phone sends a direct signal to a satellite. • The call is passed on to the telephone network. • Satellite links work well for one-way transmissions • Long term delays are common in two-way transmissions.

  14. Section 3:Radio Communication • Television Satellites • The satellite-reception dishes that you sometimes see in yards • Communications satellites use microwaves rather than the longer-wavelength radio waves used for normal television broadcasts. • Short wavelength microwaves travel more easily through the atmosphere. • The ground receiver dishes are rounded to focus the waves onto an antenna.

  15. Section 3:Radio Communication • The Global Positioning System • Helps lost hikers • GPS is a system of satellites, ground monitoring stations and receivers that determine your location. • Often four or five of the satellites are needed to show your location.

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