The frequency range suitable for beyond-the-horizon communication using sky waves is:

In a communication system operating at a wavelength of $800 \,nm$, only $1 \%$ of the source frequency is available as signal bandwidth. The number of channels accommodated for transmitting $TV$ signals of bandwidth $6 \,MHz$ is

The height of a transmitting antenna at the top of a tower is $25 \; m$ and that of the receiving antenna is $49 \; m$. The maximum distance between them for satisfactory communication in $LOS$ (Line of Sight) is $K \sqrt{5} \times 10^{2} \; m$. The value of $K$ is $\dots$ [Assume radius of Earth is $64 \times 10^{5} \; m$] (Calculate up to the nearest integer value).

$A$ carrier wave of peak voltage $60 \,V$ is used to transmit a message signal. Then the peak voltage of the modulating signal in order to have a modulation index of $90 \%$ is (in $\,V$)

If a transmitting antenna of height $105 \,m$ is placed on a hill, then its coverage area is (in $\,km^2$)

Match List-$I$ with List-$II$:

List-$I$	List-$II$
$A$. Television signal	$I$. $03\,KHz$
$B$. Radio signal	$II$. $20\,KHz$
$C$. High Quality Music	$III$. $02\,MHz$
$D$. Human speech	$IV$. $06\,MHz$

Choose the correct answer from the options given below: