For sky wave propagation of a $10\, MHz$ signal, what should be the minimum electron density in the ionosphere?

An audio signal consists of two distinct sounds: one is a human speech signal in the frequency band of $200\,Hz$ to $2700\,Hz,$ while the other is a high-frequency music signal in the frequency band of $10200\,Hz$ to $15200\,Hz.$ The ratio of the $AM$ signal bandwidth required to send both the signals together to the $AM$ signal bandwidth required to send just the human speech is

The height of a $TV$ tower is $150 \ m$. If the population density in the area covered by the $TV$ tower is $50 \ \text{lakhs}$, then the population density around the $TV$ tower is ....... $km^{-2}$. (Radius of the Earth is $6.4 \times 10^{6} \ m$)

$A$ carrier wave of peak voltage $14\,V$ is used for transmitting a message signal. The peak voltage of the modulating signal required to achieve a modulation index of $80\%$ will be.......$V$

The characteristic impedance of a coaxial cable is of the order of .......... $\Omega$.

An amplitude modulated signal is plotted below. Which one of the following best describes the above signal?