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

The layer of the atmosphere which efficiently reflects high frequency waves particularly at night is

$A$ radar has a power of $1 \ kW$ and is operating at a frequency of $10 \ GHz$. It is located on a mountain top of height $500 \ m$. The maximum distance up to which it can detect an object located on the surface of the earth (Radius of earth $= 6.4 \times 10^6 \ m$) is ....... $km$.

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

An amplitude modulated signal is plotted below. Which one of the following best describes the above signal?

If the height of the transmitting tower is increased by $30 \%$,then the area covered by it increases by (in $\%$)