An antenna of length $3 \ m$ will effectively radiate which frequency?

The process of superimposing low-frequency signals onto high-frequency carrier waves is called ..........

Match Column $A$ (layers in the ionosphere for skywave propagation) with Column $B$ (their height range).

Column $A$	Column $B$
$A$. $D$-layer	$I$. $250-400 \ km$
$B$. $E$-layer	$II$. $170-190 \ km$
$C$. $F_1$-layer	$III$. $95-120 \ km$
$D$. $F_2$-layer	$IV$. $65-75 \ km$

Which of the following is the disadvantage of $FM$ over $AM$?

Given the electric field of a complete amplitude modulated wave as $\vec E = \hat i E_c (1 + \frac{E_m}{E_c} \cos \omega_m t) \cos \omega_c t$,where the subscript $c$ stands for the carrier wave and $m$ for the modulating signal. The frequencies present in the modulated wave are:

In an $FM$ system, a $7 \ kHz$ signal modulates a $108 \ MHz$ carrier such that the frequency deviation is $50 \ kHz$. The carrier swing is: (in $kHz$)