In a frequency modulated wave:

$A$ transmitting antenna of height $20 \,m$ and a receiving antenna of height $h$ are separated by a distance of $40 \,km$ for satisfactory communication in line-of-sight $(LOS)$ mode. The value of $h$ is (Given: radius of Earth is $6400 \,km$). (in $\,m$)

$A$ transmitting antenna can cover an area of $6.4\pi \times 10^9 \ m^2$ when used for broadcasting. If the signal is transmitted to another antenna,which is at a distance of $100 \ km$ from this antenna,what should be the minimum height of the receiving antenna for satisfactory communication in line-of-sight mode (in $m$)? (Assume the radius of the Earth $R = 6400 \ km$)

In an amplitude modulated signal,the maximum amplitude is $15 V$ and the minimum amplitude is $5 V$. The amplitude of the modulating wave will be (in $V$)

In satellite communication,the uplink frequency band used is

The mathematical form of an $AM$ wave is given by $e = 50 (1 + 0.5 \sin(2\pi \times 5 \times 10^{3} t)) \sin(31.4 \times 10^{6} t) \text{ V}$. The modulation index of the given $AM$ wave is .......