In a receiver, an RF amplifier is generally used to amplify the tiny signal (i.e., microvolts) arriving from the antenna. As those signals are really weak, the first amplifier stage must introduce as little supplementary noise as possible. Once amplified, the incoming signal is fed to the mixer.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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In a receiver, an RF amplifier is generally used to amplify the tiny signal (i.e., microvolts) arriving from the antenna. As those signals are really weak, the first amplifier stage must introduce as little supplementary noise as possible. Once amplified, the incoming signal is fed to the mixer.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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The mixer in a receiver takes in the incoming signal and mixes it with a local oscillator to transpose (usually down) the incoming signal to a fixed intermediate frequency (the Superheterodyne concept). Using a fixed and lower intermediate frequency regardless of operating frequency facilitates the achievement of high gain and selectivity. Changing the operating frequency is a simple matter of changing the frequency of the local oscillator.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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The mixer in a receiver takes in the incoming signal and mixes it with a local oscillator to transpose (usually down) the incoming signal to a fixed intermediate frequency (the Superheterodyne concept). Using a fixed and lower intermediate frequency regardless of operating frequency facilitates the achievement of high gain and selectivity. Changing the operating frequency is a simple matter of changing the frequency of the local oscillator.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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As opposed to the front-end that can be relatively wide, the IF chain in a superheterodyne receiver sets the final bandwidth so only one channel is received at a time.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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In a superheterodyne receiver, the intermediate frequency chain supplies most of the gain and detection is performed on the amplified intermediate frequency signal.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Detection (recovery of the original message) in a frequency modulation receiver is performed by the 'discriminator'. The discriminator translates frequency deviation back to audio. Early discriminators were sensitive to amplitude variations and needed to be preceded by a 'limiter' to remove amplitude variations from the received signal. Limiters are an integral part of an FM system, as they cut down the influence of noise.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Detection (recovery of the original message) in a frequency modulation receiver is performed by the 'discriminator'. The discriminator translates frequency deviation back to audio. Early discriminators were sensitive to amplitude variations and needed to be preceded by a 'limiter' to remove amplitude variations from the received signal. Limiters are an integral part of an FM system, as they cut down the influence of noise.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Most receivers rely on an audio amplifier to provide sufficient volume from the loudspeaker.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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In an FM receiver, a very large gain is required ahead of the limiter so it can work effectively. The consequence of that gain is a very loud noise in the absence of a signal at the operating frequency. To counter that annoyance, a "squelch" circuit is included in the audio stage to silence the noise in the absence of a signal.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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