Amateur ExtraE7B07

Which of the following is the likely result of using a Class C amplifier to amplify a single-sideband phone signal?

D
Answer
Practical circuits and system design
Type
A
Reduced intermodulation products
B
Increased overall intelligibility
C
Reduced third-order intermodulation
D
Signal distortion and excessive bandwidth

Answer Notes

Class C amplifiers are highly efficient because their transistors or tubes conduct for less than 180 degrees (less than half) of the input signal cycle. However, this extreme non-linearity makes them completely unsuitable for amplifying signals with varying amplitude, such as Single Sideband (SSB) or AM phone signals. If you feed an SSB signal through a Class C amplifier, the delicate amplitude variations representing the human voice will be severely clipped. This clipping produces massive signal distortion and generates severe intermodulation products. These intermodulation products will splatter your transmission across a wide frequency range, causing excessive bandwidth and interfering with adjacent stations. SSB requires a linear amplifier, such as Class A or AB.
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