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

$A$ transmitting antenna can cover an area of $6.4\pi \times 10^9 \ m^2$ when used for broadcasting. If the signal is transmitted to another antenna,which is at a distance of $100 \ km$ from this antenna,what should be the minimum height of the receiving antenna for satisfactory communication in line-of-sight mode (in $m$)? (Assume the radius of the Earth $R = 6400 \ km$)

Digital signal

Ultra high frequency $(UHF)$ band stands for

$A$ $TV$ tower has a height of $100 \ m$. The average population density around the tower is $1000 \ \text{per} \ km^2$. The radius of the earth is $6.4 \times 10^6 \ m$. The population covered by the tower is:

In frequency modulation,