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Build Your Own Transistor Radios by Ronald Quan

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Chapter 22Noise

This chapter covers the basic concepts behind random noise (e.g., hiss). In radio circuits, the noise in a front-end circuit hampers the ability to pick out weak radio-frequency (RF) signals. In audio circuits, the noise sources degrade the signal-to-noise ratio in mostly preamp circuits such as microphone preamplifiers. However, as mentioned in Chapter 12, where op amps and mixers are used in software-defined radio (SDR) front-end circuits, the noise contribution not only from the mixer circuits but also from the intermediate-frequency (IF) amplifiers can hamper reception of weak signals. In this chapter, the examination of noise will be limited to amplifier circuits and not mixers.

Therefore, the objectives for this chapter ...

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