E8A06: PEP-to-average ratio: Approximate ratio of PEP-to-average power

Q: 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 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.

Updated: Dec 9, 2025 | Source: 2024-2028 Question Pool | Topic: E8A

E8A06E8A

What is the approximate ratio of PEP-to-average power in an unprocessed single-sideband phone signal?

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Deep Dive: E8A06

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.

Why Other Answers 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.

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 Example

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.

Source & Coverage

Question Pool: 2024-2028 Question Pool

Subelement: E8A

Reference: FCC Part 97.313

Key Concepts

PEP-to-average ratio SSB phone Peak envelope power Average power

Verified Content

Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E8A topic.