6.9 How radio worksApril 21, 2023

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 Oscillator Modulator Amplifier

Microphone

AF signal

RF carrier Modulated RF carrier

Sending sounds by radio

Amplifier demodulator Tuning circuit

Loudspeaker

AF signal Modulated RF carrier

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