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Home » Figure shows a communication system. What is the output power when the input signal is of 1.01mW? (gain in dB = 10 log10 (Po /Pi ).
Figure shows a communication system. What is the output power when the input signal is of 1.01mW? (gain in dB = 10 log10 (Po /Pi ).
CBSE | Class 12 | Communication Systems | NCERT Exemplar | Physics
Figure shows a communication system. What is the output power when the input signal is of 1.01mW? (gain in dB = 10 log10 (Po /Pi ).

Exemplar Solutions Class 12 Physics Chapter 15 - 3

Answer:

It is given that there is a loss of signal 2dB per km.
So total loss suffered in 5km = -2 x 5 = -10 dB.
In both input and output amplifiers, the total gain of the signal is given by:
So the overall gain of the output signal is
 dB  dB
Gain dB
We have to calculate the output power. We have:

  {{P}_{i}}=1.01mW

dB=10{{\log }_{10}}\left( \frac{{{P}_{0}}}{{{P}_{i}}} \right)

20=10{{\log }_{10}}\left( \frac{{{P}_{0}}}{{{P}_{i}}} \right)

2=\log \frac{{{P}_{0}}}{{{P}_{i}}}

100=\frac{{{P}_{0}}}{{{P}_{i}}}

{{P}_{0}}=100\times {{P}_{i}}=100\times 1.01mW

{{P}_{0}}=101mW

i

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