$A$ square wave of the modulating signal is shown in the figure. The carrier wave is given by $C(t) = 5 \sin(8\pi t) \text{ V}$. The modulation index is:

In amplitude modulation,the sinusoidal carrier frequency is denoted by $\omega_c$ and the signal frequency is denoted by $\omega_m$. The bandwidth of the signal is such that $\omega_m << \omega_c$. Which of the following frequencies is not contained in the modulated wave?

$A$ message signal of frequency $20 \, kHz$ and peak voltage of $20 \, V$ is used to modulate a carrier wave of frequency $1 \, MHz$ and peak voltage of $20 \, V$. The modulation index will be ..... .

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

$A$ carrier is simultaneously modulated by two sine waves with modulation indices of $0.3$ and $0.4$; then the total modulation index is

$A$ $TV$ transmitting antenna is $98\,m$ high and the receiving antenna is at the ground level. If the radius of the earth is $6400\,km$,the surface area covered by the transmitting antenna is approximately $.........\,km^2$