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

The radio horizon of the transmission of an antenna placed on the $20^{\text{th}}$ floor in a shopping mall,where the height of each floor is $2 \,m$,is (Radius of Earth is $6.4 \times 10^6 \,m$): (in $\,km$)

Range of frequencies allotted for commercial $FM$ radio broadcast is

For transmitting a signal of frequency $1 \text{ kHz}$,the wavelength of the wave should be:

$A$ $TV$ transmission tower of height $h$ covers a range of distance $d$. By how much will the range change if the height is increased to $3/2 h$?

The process of recovering the modulating signal from the modulated carrier wave is called: