Discussion
A receiver has a sensitivity of \( 10 \ \mathrm{\mu V} \) and an antenna delivering \( 40 \ \mathrm{\mu V} \). The margin is about
Answer: B
Taking the voltage ratio in decibels:
\[ 20\log_{10}\left(\frac{40}{10}\right) = 12 \ \mathrm{dB} \]
giving 12 dB of margin. 4 dB is the ratio itself misread as decibels. 30 dB corresponds to a ratio of about thirty. And 6 dB would be a ratio of two. Remembering that voltage ratios take twenty times the logarithm, and power ratios ten, is the single most useful habit in receiver work.
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