A simplest antenna is a single piece of metal wire attached to a radio circuit. The first radio I ever built when iam pursuing my diploma in Electronics & Communication Engg , when I was 19, was a crystal set with a long loop of copper wire acting as the antenna. The signals on these different wave bands are carried by radio waves of different frequency and wavelength.
I have built a simple FM radio transmitter circuit on bread board, i have taken the circuit diagram from EFY website magazine and purchased all electronic components from store. Below are the images which defines the basic antenna working methodology.