Amplitude modulation has

The size of the antenna required for a carrier wave of frequency $3 \text{ MHz}$ is: (in $\text{ m}$)

$A$ 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 ....... $km$.

In a line of sight radio communication,a distance of about $50\, km$ is kept between the transmitting and receiving antennas. If the height of the receiving antenna is $70\, m$,then the minimum height of the transmitting antenna should be........$m$ (Radius of the Earth $= 6.4 \times 10^6\, m$)

For sky wave propagation of a $10\, MHz$ signal, what should be the minimum electron density in the ionosphere?

$A$ signal of frequency $20 \, kHz$ and peak voltage $5 \, V$ is used to modulate a carrier wave of frequency $1.2 \, MHz$ and peak voltage $25 \, V$. Choose the correct statement.