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Question
Figure shows a communication system. What is the output power when input signal is of 1.01 mW? (gain in dB = 10 log10 (Po/Pi).
Solution
Here, transmission = 5 km
Loss suffered in transmission path = – 2d Bkm–1 × 5 km = – 10 db
Total amplifier gain = 10 dB + 20 dB = 30 dB
Over gain of signal = 30 dB – 1 dB = 20 dB
∴ 20 = 10 log10 .....(P0/P1)
or log10 .....(P0/P1) = `20/10` = 2 = log10 100 P0/Pt =100
or P0 = Pt × 100 = 1.01 mW × 100 = 101 mW.
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