In satellite communication,the $6\,\text{GHz}$ frequency is used for........... and the $4\,\text{GHz}$ frequency is used for...........

For $100\%$ modulation $(AM)$,the useful part of the total power radiated is

$A$ transmitting antenna is kept on the surface of the earth. The minimum height of the receiving antenna required to receive the signal in line-of-sight at $4\,km$ distance from it is $x \times 10^{-2}\,m$. The value of $x$ is (Let radius of earth $R = 6400\,km$).

$A$ carrier signal $60 \sin(2\pi \times 10^6 t)$ is used to modulate an audio signal $15 \sin(300 \pi t)$. The depth of modulation is .......... $\%$.

The maximum peak-to-peak voltage of an $AM$ wave is $24 \, mV$ and the minimum peak-to-peak voltage is $8 \, mV$. The modulation factor is.....$\%$

The government has divided the frequency range from $30\ MHz$ to $60\ MHz$ between $20$ stations,which are independently beaming their signals. Which of the signals can be beamed by each of the stations?