If $f_m$ is the modulation frequency for $FM$,then the modulation index is proportional to.....

In a communication system,a repeater is used to extend the range of transmission. It is a combination of:

$A$ carrier wave of peak voltage $12 \,V$ is used to transmit a signal. If the modulation index is $75 \%$, the peak voltage of the modulating signal is (in $\,V$)

When the angle of incidence is $74^{\circ}$,the critical frequency of the $F$ layer is $50 \text{ MHz}$. What is the Maximum Usable Frequency $(MUF)$ in $\text{ MHz}$ (in $.5$)?

$A$ transmitting antenna is kept on the surface of the earth. The minimum height of the receiving antenna required to receive the signal in line-of-sight at $4\,km$ distance from it is $x \times 10^{-2}\,m$. The value of $x$ is (Let radius of earth $R = 6400\,km$).

Basically,the product modulator is