61 lines
1.6 KiB
Markdown
61 lines
1.6 KiB
Markdown
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---
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tags: [radio, ham-study]
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---
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# Radio transmitters and receivers
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## Transmitters
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Radio transmission comprises four stages:
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1. Audio stage or "amplification"
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- The weak signals from the microphone are amplified
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2. Frequency generation via an oscillator
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- The [carrier wave](./Frequency_modulation.md) is generated
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3. Modulation
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- The carrier wave and audio signal are combined
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4. RF power amplification
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- The combined signal is increased and fed through to the antenna
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The following are important considerations:
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> Incorrect setting of the oscillator can result in operation outside of the
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> amateur band and cause interference to other users
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> The microphone gain should not be set too loud as this will cause distortion.
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> Furthermore, too loud a signal causes **over-modulation** on AM and
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> **over-deviation** on FM which again could cause inteference.
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> The RF power amplifier must be connected to a correctly matched antenna to
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> work properly. If not, damage can be caused to the transmitter.
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## Receivers
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Radio reception comprises three stages:
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1. Tuning/RF amplifier
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- The receiver is tuned to the required frequency and the weak incoming signal
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is amplified so that it can be used
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2. Demodulator
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- Extracts the original audio signal from the modulated radio signal, separating
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the signal from the carrier.
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- Each type of modulation type (FM, AM, SSB etc) has its own demodulator
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3. Audio amplifier
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- Amplifies the recovered signal and feeds it to a loudspeaker or headphones
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