Figure shows a communication system. Which is the output power when input signal is 1.01 mW? (Gain in dB=\(10\log { _{ 10 }\frac { { P }_{ 0 } }{ { P }_{ 1 } } } \))

Consider an optical communication system operating at = 800nm. Suppose only 1% of optical source frequency is the available channel bandwidth for optical communication. How many channels can be accommodated for transmitting 
(i) audio signals requiring a bandwidth of 8kHz?
(ii) video TV signals requiring an approximate bandwidth of 4.5MHz? Support your answer with suitable calculations.

An audio signal is modulated by a carrier wave of 20 MHz such that the bandwidth required for modulation is 3kHz.Could this wave be demodulated by a diode detector which has the values of R and C as
 (i) R=\(1k\Omega ,C=0.01\mu F\)
 (ii) R=\(10k\Omega ,C=0.01\mu F\)
 (iii) R=\(10k\Omega ,C=1\mu F\)

Distinguish between 'sky waves' and 'space waves' modes of propagation in communication system.
(a) Why is sky wave mode propagation restricted to frequencies upto 40 MHz?
(b) Give two examples where space wave mode of propagation is used.

Describe briefly, by drawing suitable diagrams, the (i) sky wave and (ii) space wave modes of propagation. Mention the frequency range of the waves in these modes of propagation.