Question
How does a signal that reads 20 dB over S9 compare to one that reads S9 on a receiver, assuming a properly calibrated S meter?
Answer Options
- A) It is 10 times less powerful
- B) It is 20 times less powerful
- C) It is 20 times more powerful
- D) It is 100 times more powerful
Correct Answer: D
Explanation
The decibel (dB) scale is logarithmic, meaning it expresses a ratio of two power levels. For a properly calibrated S meter, S9 is generally defined at a specific microvolt level (often 50 \mu\text{V} for HF), and the scale above S9 is marked in \text{dB} units.
Since 10 \text{dB} represents a factor of 10 in power, a 20 \text{dB} increase represents 10 \times 10, or a factor of 100 in power. Therefore, a signal reading 20 \text{dB} over S9 is 100 times more powerful than a signal reading S9.
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