What is the approximate ratio of PEP-to-average power in an unprocessed single-sideband phone signal?
The correct answer is A: 2.5 to 1. The approximate PEP-to-average power ratio in an unprocessed single-sideband phone signal is 2.5 to 1 (2.5:1). This means peak envelope power (PEP) is about 2.5 times the average power.
This ratio comes from the nature of speech signals. Speech has peaks (like vowel sounds) and valleys (like consonants and pauses). The average power is lower than the peak power because speech isn't constant. For typical speech, PEP is about 2.5 times the average power. This ratio is important for transmitter design - you need to size the transmitter to handle PEP, but average power determines heating and power supply requirements. Processed SSB signals (with compression or clipping) can have different ratios.
Exam Tip
Unprocessed SSB PEP ratio = 2.5:1. Remember: Unprocessed SSB phone signals have a PEP-to-average power ratio of approximately 2.5 to 1. This reflects the nature of speech with peaks and valleys.
Memory Aid
"**U**nprocessed **S**SB **P**EP = **2**.**5** to **1** (think 'USP = 2.5:1')"
Real-World Application
You're operating SSB phone with 100 watts PEP. Because speech has peaks and valleys, your average power is about 40 watts (100 / 2.5 = 40). Your transmitter must handle 100 watts PEP, but your power supply and cooling only need to handle the 40-watt average. This 2.5:1 ratio is typical for natural, unprocessed speech.
FCC Part 97.313Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. 25 to 1 would be an extremely high ratio, more typical of highly processed or clipped signals, not unprocessed SSB.
Option C: Incorrect. 1 to 1 would mean PEP equals average power, which would only occur with a constant-amplitude signal, not speech.
Option D: Incorrect. 13 to 1 is way too high for unprocessed SSB. That ratio would indicate severe processing or clipping.
题目解析
The correct answer is A: 2.5 to 1. The approximate PEP-to-average power ratio in an unprocessed single-sideband phone signal is 2.5 to 1 (2.5:1). This means peak envelope power (PEP) is about 2.5 times the average power. This ratio comes from the nature of speech signals. Speech has peaks (like vowel sounds) and valleys (like consonants and pauses). The average power is lower than the peak power because speech isn't constant. For typical speech, PEP is about 2.5 times the average power. This ratio is important for transmitter design - you need to size the transmitter to handle PEP, but average power determines heating and power supply requirements. Processed SSB signals (with compression or clipping) can have different ratios.
考试技巧
Unprocessed SSB PEP ratio = 2.5:1. Remember: Unprocessed SSB phone signals have a PEP-to-average power ratio of approximately 2.5 to 1. This reflects the nature of speech with peaks and valleys.
记忆口诀
**U**nprocessed **S**SB **P**EP = **2**.**5** to **1** (think 'USP = 2.5:1')
实际应用示例
You're operating SSB phone with 100 watts PEP. Because speech has peaks and valleys, your average power is about 40 watts (100 / 2.5 = 40). Your transmitter must handle 100 watts PEP, but your power supply and cooling only need to handle the 40-watt average. This 2.5:1 ratio is typical for natural, unprocessed speech.
错误选项分析
Option B: Incorrect. 25 to 1 would be an extremely high ratio, more typical of highly processed or clipped signals, not unprocessed SSB. Option C: Incorrect. 1 to 1 would mean PEP equals average power, which would only occur with a constant-amplitude signal, not speech. Option D: Incorrect. 13 to 1 is way too high for unprocessed SSB. That ratio would indicate severe processing or clipping.
知识点
PEP-to-average ratio, SSB phone, Peak envelope power, Average power
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.