Refer to figures

Dipole antenna:

This antenna is the most widely-used type of antenna. It is the simplest form of an antenna. A basic dipole antenna, as seen in figure 1, consists of 2 conductors arranged symmetrically with one side of the balanced feedline from the transmitter or receiver attached to each.

Monopole antenna:

This antenna has a more complicated design. A monopole antenna, as seen in figure 2, consists of a single conductor, usually attached to the ground. Because of the use of only one conductor, the monopole antenna has twice the gain of a similar dipole antenna.

Loop antenna:

Loop antenna, as the name suggests, suggest of a loop of wire. Loop antennas, as seen in figure 3, correspond directly with the magnetic field of the radio wave, which means they are insensitive to electrical noise.

Quadrupole antenna:

As the name suggests, this antenna consists of 4 parts. This is the most complex form of antenna and therefore not much used. As seen in figure 4, it consists of 4 monopole antennas attached in order.