In $TV$ transmission,the audio signal is ........ modulated and the video signal is ........ modulated.

Digital signal

Which of the following four alternatives is not correct? We need modulation:

For the propagation of $10 \ MHz$ signals as sky waves,what should be the minimum electron density in the ionosphere?

If the maximum and minimum voltages of an $A.M.$ wave are $V_{\max}$ and $V_{\min}$ respectively,then the modulation factor '$m$' is

The heights of transmitting and receiving antennas are respectively $\frac{1}{20000}$ and $\frac{1}{80000}$ times the radius of the earth. The maximum distance between these two antennas for satisfactory communication in line of sight mode is (Radius of the earth $= 6.4 \times 10^6 \ m$) (in $km$)