How is antenna length determined?

A TV tower is $120 \mathrm{m}$ high, How much more height is to be added to it if its cover range is ti become double?

Are omnidirectional antennas better?

A TV tower is $80 \mathrm{m}$ tall. Calculate the maximum distance upto which the signal transmitted from the tower can be received.

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$

By what percentage will the transmission range of a TV tower be affected when the height of the tower is increased by 21%.