Changes

=== Monopole ===

* It is the simplest kind of antenna. It's just a wire and a ground plane with the wire perpendicular to ground plane. From electromagnetic theory, the ground plane acts as a mirror and the monopole antenna acts as a dipole antenna of twice its length. Hence most of its properties are same as a dipole antenna of twice length

* The main points of difference between a monopole and dipole are its resonant length, input impedance and directivity. A dipole resonates at 0.48 fraction of wavelength while the monopole resonates at half this length as monopole acts as a dipole twice its length. The input impedance of monopole is half of a dipole of twice length i.e. 36.5 + j21.25 ohm (for length 0.25*wavelength). The directivity of monopole is twice (+3 in dB) of dipole antenna i.e. 5.15 dB.