Transcript Review knowledge of AC State the difference between

2 April 2016
6.9 How radio works
What is this image? What
other information can
you get from it?
Aims
• Review knowledge of AC
• State the difference between AM and FM
• Describe how a simple radio works
Sending sounds by radio
RF carrier
Modulated RF carrier
RF Oscillator
Modulator
Amplifier
AF signal
Microphone
Sending sounds by radio
AF signal
Modulated RF carrier
Amplifier
demodulator
Loudspeaker
Tuning circuit
Radio gaga
• AF signal: varying voltage
• RF oscillator creates high frequency AC, this is the
carrier
• AF signals modulate the RF waves
• RF wave is then amplified
• RF waves then generate a voltage in the aerial
• The tuning circuit decides which frequency of RF
carrier to detect
• The demodulator then removes the carrier wave
leaving on AF
• This is amplified and then converted to sound
AM and FM
• This is amplitude modulation or AM
• You can also use frequency modulation (FM)
• FM has less noise so this is better