Question
What dB change represents a factor of two increase or decrease in power?
Answer Options
- A) Approximately 2 dB
- B) Approximately 3 dB
- C) Approximately 6 dB
- D) Approximately 9 dB
Correct Answer: B
Explanation
The decibel (\text{dB}) is a logarithmic unit used to express a ratio of two power levels, which makes large ratios easier to handle. The formula for the power ratio in \text{dB} is 10 \log_{10}(P_2/P_1). To find the \text{dB} change for a factor of two power increase (i.e., P_2/P_1 = 2), the calculation is 10 \log_{10}(2).
Performing this calculation yields approximately 3.01 \text{ dB}. Therefore, a change of approximately 3 \text{ dB} represents a doubling (or halving) of power. This is a fundamental relationship in electronics and is widely used in amateur radio for power measurements, such as antenna gain or feed line loss.
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