Antennas
Electromagnetic Radiation
The magnetic field lines are in red
The electric field lines are in blue
The inductance and capacitance (together with the implied excitation energy) comprise a tuned circuit.
This dynamic representation above depicts electromagnetic radiation illustrating how the plates of a capacitor relate
to the elements of a dipole antenna. Not shown is the wave nature of the radiation fields and their 90° relationship to each other.
The electric and magnetic energy in an electromagnetic wave are in phase with each other and polarized at ninety degrees to each other
with the electric field being vertically polarized, and the magnetic field horizontal in these graphic examples.
Below are shown the vertical electric field (blue) and the
horizontal magnetic field (red) with their magnitudes varying sinusoidally with time on the X axis.
Above is a dynamic illustration of the magnetic and electric fields shown in the static image above it (albeit with colors reversed).
Above is another dynamic illustration of the magnetic and electric fields of an electromagnetic wave.
The above picture shows how several quantities on and near a half-wave dipole vary over time. These quantities are indicated by different colors:
Currents: blue lines, length proportional to magnitude.
Charges: cyan (positive), magenta (negative).
Electric field vectors: red lines.
Magnetic field vectors: green lines.
The dipole antenna itself is on the Y-axis, bottom left corner. Electric and magnetic field strength calculated only in the first quadrant of the YZ-plane.
Due to symmetry, other quadrants don't significantly add to visualization. Electric field vectors lie in the YZ-plane, magnetic field is perpendicular.
The SWR plots on the antenna pages were created with the LP-Plot utility program kindly provided by Larry Phipps, manufacturer of the LP-100A digital vector wattmeter.