The minimum size of an antenna for transmitting electromagnetic waves at $1500 \text{ MHz}$ is

Indicate which one of the following systems is digital.

The physical sizes of the transmitter and receiver antenna in a communication system are

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 $= 6.4 \times 10^6\, m$)

$A$ carrier wave of peak voltage $20 V$ is used to transmit a message signal. For getting a modulation index of $60 \%$, the peak voltage of the modulating signal is (in $V$)

The height of an antenna is $500 \ m$. Its range is ........ $km$. (Radius of the Earth is $6400 \ km$)