$A$ message signal of $12 kHz$ and peak voltage $20 V$ is used to modulate a carrier wave of frequency $12 MHz$ and peak voltage $30 V$. Then,the modulation index is

The transmitting antenna placed at the top of a tower has a height of $45 \ m$ from the ground. The distance between receiving and transmitting antennas is $40 \ km$ and the radius of earth is $6400 \ km$. The minimum height (in $m$) at which the receiving antenna is to be placed for satisfactory communication in $LOS$ mode, is

At a particular station,the $TV$ transmission tower has a height of $100\,m$. To triple its coverage range,the height of the tower should be increased to ......$m$.

Coaxial cable,a widely used wire medium,offers an approximate frequency bandwidth of:

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:

Two identical antennas mounted on identical towers are separated from each other by a distance of $45 \, km$. What should be the minimum height of the receiving antenna to receive the signals in line of sight? (Assume radius of earth is $6400 \, km$)