The bandwidth of a coaxial cable system is approximately........ $MHz$.

$AM$ (Amplitude Modulation) is used for broadcasting because

In the process of modulation,........

The digital signals are used for transmission in communication systems. They are

The electron density of $E, F_1, F_2$ layers of the ionosphere is $2 \times 10^{11} \, m^{-3}$,$5 \times 10^{11} \, m^{-3}$,and $8 \times 10^{11} \, m^{-3}$ respectively. What is the ratio of critical frequencies for the reflection of radio waves?

The radio horizon of a transmitting antenna of height $39.2 \ m$ is (Radius of the earth $= 6400 \ km$) (in $km$)