Simple Antennas
By far the simplest antenna is the Long wire antenna. As the name
implies it is little more then a long wire run in a straight line and then
in to the back of the receiver unit such as a radio. This type of
antenna has one advantage it is simple easy and cheap to make to make it
was the first type of antenna made. However it has many disadvantages.
It is very large and therefore can't be moved around and because it is
untuned (more on what this means later) it picks up signals of many wave
lengths. This means it often picks up other signals that are not
wanted such as electric sparks and other meaningless signals.
Half Wavelength Antennas
To avoid these problems it is better to make an antenna that is tuned or
able to pick up only a limited range of wave lengths. By making the
antenna half as long as one wavelength the antenna becomes selective only
picking up a small range of wavelengths. This type of antenna however
requires a ground this is used in the form of a ground plane which is formed
by other antennas a right angles to the bottom of the vertical arial these
horizontal ground arials are atached to a ground. This is the sort
of antenna used on cars, however in that use that cars metal body forms
the ground plane.
The half wave antenna is used in many forms often more then one will
be used togeather to increase the signal stringth. In many cases
inductors or loops of wire are added to change the effective length or
to focus the wavelength more.
Home
Back to Electromagnetic Waves
Forward to Complex Antennas