Question
What is the approximate ratio of PEP-to-average power in an unprocessed single-sideband phone signal?
Answer Options
- A) 2.5 to 1
- B) 25 to 1
- C) 1 to 1
- D) 13 to 1
Correct Answer: A
Explanation
Peak Envelope Power (\text{PEP}) is the maximum power achieved at the peak of the \text{RF} envelope during a single cycle of the modulating wave. Average power is the power averaged over an entire modulation cycle. For a constant carrier, like \text{CW}, \text{PEP} and average power are equal (1:1 ratio).
However, a Single-Sideband (\text{SSB}) voice signal is complex, with energy concentrated in short bursts corresponding to voice peaks. For an unprocessed (uncompressed or unclipped) \text{SSB} phone signal modulated by a typical voice, the power ratio is highly variable but approximately 2.5 to 1 (\text{PEP} is 2.5 times the average power). This ratio is why an \text{SSB} transmitter can run a higher \text{PEP} than its average power capability.
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