A transmitting antenna is kept on the surface of the Earth. The minimum height of receiving antenna required to receive the signal in line of sight at $$4 \mathrm{~km}$$ distance from it is $$x \times 10^{-2} \mathrm{~m}$$. The value of $$x$$ is

A TV tower has a height of $$75 \mathrm{~m}$$. What is the maximum distance upto which this TV transmission can be received? (Take, radius of the earth $$=6.4 \times 10^6 \mathrm{~m}$$)

The demodulator or detector circuit consists of a