In communication system, a repeater is used to extend the range to transmission. It is the combination of

In amplitude modulation, the amplitude of carrier wave is $A_c$ and that of the modulating signal is $A_m$. In practice, the ratio of $A_m$ to $A_c$ is kept less than or equal to one, to avoid

In frequency modulated wave

A layer of atmosphere that reflects medium frequency radio waves which is ineffective during night, is