If the range of a $TV$ telecast is to be doubled,the height of the transmitting antenna must be:

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

List-$I$	List-$II$
$A$. Troposphere	$I$. Approximate $65-75 \ km$ over Earth's surface
$B$. $E$-Part of Ionosphere	$II$. Approximate $300 \ km$ over Earth's surface
$C$. $F_2$-Part of Ionosphere	$III$. Approximate $10 \ km$ over Earth's surface
$D$. $D$-Part of Ionosphere	$IV$. Approximate $100 \ km$ over Earth's surface

Choose the correct answer from the options given below:

Which of the following options is $NOT$ correct? We need modulation for:

For effective radiation of a wave with a frequency of $20 \text{ MHz}$,what should be the length of the antenna in $m$?

In a communication system,what is used to extend the range of a communication?

In an amplitude modulator circuit,the carrier wave is given by $C(t) = 4 \sin(20000 \pi t)$ and the modulating signal is given by $m(t) = 2 \sin(2000 \pi t)$. The values of the modulation index and the lower sideband frequency are: