2-2
ELECTROMAGNETIC FIELDS
The way energy is propagated into free space is a source of great dispute among people concerned
with it. Although many theories have been proposed, the following theory adequately explains the
phenomena and has been widely accepted. There are two basic fields associated with every antenna; an
INDUCTION FIELD and a RADIATION FIELD. The field associated with the energy stored in the
antenna is the induction field. This field is said to provide no part in the transmission of electromagnetic
energy through free space. However, without the presence of the induction field, there would be no
energy radiated.
INDUCTION FIELD
Figure 2-1, a low-frequency generator connected to an antenna, will help you understand how the
induction field is produced. Let's follow the generator through one cycle of operation.
Figure 2-1.—Induction field about an antenna.
