If the length of an antenna is $150 \,cm$,the transmission frequency is . . . . . . $MHz$. (Speed of light in vacuum $= 3 \times 10^8 \,ms^{-1}$)

Which of the following is not a natural source of electrical noise?

Ultra high frequency $(UHF)$ band stands for

If the highest frequency modulating a carrier is $5\, kHz$,then the number of $AM$ broadcast stations accommodated in a $90\, kHz$ bandwidth are ....... .

$A$ radar has a power of $1 \text{ kW}$ and operates at a frequency of $10 \text{ GHz}$. If it is located on top of a mountain at a height of $500 \text{ m}$,what is the maximum distance in $\text{km}$ up to which it can detect objects on the Earth's surface? (Radius of the Earth $R = 6.4 \times 10^{6} \text{ m}$)

For an amplitude-modulated wave,the maximum amplitude is $9 \ V$ and the minimum amplitude is $3 \ V$. The modulation index is ........$\%$.