37 lines
1.2 KiB
Markdown
37 lines
1.2 KiB
Markdown
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---
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tags: [radio, ham-study]
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---
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# Radio signal modulation
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A radio signal comprises two parts:
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- the message (information)
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- the frequency for transmission of the information (the carrier)
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The process of adding information (an audio signal) to a carrier is called
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**modulation**.
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## Amplitude modulation (AM)
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The message is combined with a carrier on a set frequency.
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When the message is added to the carrier wave, the amplitude of the wave form
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varies depending on the volume of the audio signal.
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## Frequency modulation (FM)
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Again the audio signal is combined with a carrier on a set frequency however the
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amplitude of the resulting signal remains constant. The freequency changes
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relative to the volume of the audio signal. When the volume of the audio signal
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is louder, the waves are closer together. In other words, the frequency of the
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waves per second increases.
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## Continuous wave modulation (CW - Morse code)
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A continous wave has a constant amplitude and frequency. To send information you
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simply switch this wave on and of. When it is on, the radio wave is transmitted.
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When it is off, nothing is transmitted.
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This is the basis for communication using Morse code over radio waves.
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