Antenna To transmit radio waves, an AC generator is placed at the midpoint of an antenna. As AC current builds and collapses in the antenna, a magnetic  field also builds and collapses around it. An electric field also builds and subsides as the voltage shifts  from one end of the antenna to the other. Both fields, the magnetic and the electric, fluctuate around the  antenna at the same time. The antenna is ½ the wavelength of the AC signal received  from the generator. At any one point along the antenna, voltage and current vary inversely to each other. Generator Magnetic field I Magnetic  field Electric field I Electric field Current Voltage 2 Figure 11-76.  Radio waves are produced by applying an AC signal to an antenna. This creates a magnetic and electric field around the  antenna. They build and collapse as the AC cycles. The speed at which the AC cycles does not allow the fields to completely collapse  before the next fields build. The collapsing fields are then forced out into space as radio waves.  11-33