When you tune in your radio you are listerning to information sent by a broadcaster as a carrier wave. There are however two ways to modulate this underlying carrier wave signal. On your radio there will be an AM/FM switch to swap between radio stations that use these two methods.
FM radio works the same way that AM radio works. The difference is in how the carrier wave is modulated, or altered. With AM radio, the amplitude, or overall strength, of the signal is varied to incorporate the sound information. With FM, the frequency (the number of times each second that the current changes direction) of the carrier signal is varied.
FM signals have a great advantage over AM signals. Both signals are susceptible to slight changes in amplitude. With an AM broadcast, these changes result in static. With an FM broadcast, slight changes in amplitude don't matter -- since the audio signal is conveyed through changes in frequency, the FM receiver can just ignore changes in amplitude. The result: no static at all.
Digital radio only needs to carry on/off digital information, like a computer or a cd, so digital radio uses the AM system.
FM radio works the same way that AM radio works. The difference is in how the carrier wave is modulated, or altered. With AM radio, the amplitude, or overall strength, of the signal is varied to incorporate the sound information. With FM, the frequency (the number of times each second that the current changes direction) of the carrier signal is varied.
FM signals have a great advantage over AM signals. Both signals are susceptible to slight changes in amplitude. With an AM broadcast, these changes result in static. With an FM broadcast, slight changes in amplitude don't matter -- since the audio signal is conveyed through changes in frequency, the FM receiver can just ignore changes in amplitude. The result: no static at all.
Digital radio only needs to carry on/off digital information, like a computer or a cd, so digital radio uses the AM system.
Radio waves like all other forms of electromagnetic radiation travel at the speed of light (300 000 000m/s).
Our wave equation says that:
velocity (metres per second) = frequency (hertz Hz) x wavelength (metres)
which can be written i short as: v= f ƛ
Radio stations normally give their frequencies in KiloHertz. For example ABC Melbourne is on 774 KHz so has a wavelength of 300 000 000 / 774 000 = 388m
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