Which of the following is not a basic component of a communication system?

The bandwidth of an audio signal is approximately:

What is the modulation index of an over-modulated wave?

The height of a transmitting antenna is $h \ m$ and the height of a receiving antenna is $45 \ m$. The distance between them is $40 \ km$. For satisfactory $Line\, of\, Sight$ $(LOS)$ communication between the two antennas,the height of the transmitting antenna $h$ must be ....... $m$. (Radius of the Earth $R = 6400 \ km$)

The frequency of a $FM$ transmitter without signal input is called

The ratio of the maximum amplitude to the minimum amplitude of an amplitude-modulated wave is $4$. What is the modulation index of this wave?