In the case of amplitude modulation,to avoid distortion,the modulation index $(\mu)$ should be:

$A$ message signal is super-imposed with a carrier signal. The resulting modulating signal $C_m(t)$ is given by $C_m(t)=A_1 \sin \left(\omega_1 t\right)+A_2 \sin \left(\omega_2 t\right)-A_2 \sin \left(\omega_3 t\right)$,where $\omega_2 < \omega_1 < \omega_3$. The modulation index and the angular frequency of the message signal respectively,are

In a modulation process where the pulse duration varies with the modulating signal,it is called ......

The process of the loss of strength of a signal while propagating through a medium is known as:

$A$ layer of the atmosphere that reflects medium-frequency radio waves and is ineffective during the night is

Which one of the following is not classified as pulse modulation?