Home Electromagnetic Waves Reflection References
Antennas generate
or
collect electromagnetic energy. There are many
different types of antennas but only two basic radiating
patterns: omni directional and directional. The radiating
pattern required often is dependent on the type of wave to be
propagated or the position of the target receiver(s). For
example, a home internet satellite transmit antenna produces a focused
beam of energy in one direction but a cellular telephone antenna
produces an omni-directional output.
Regardless of the type of antenna, it must be designed so that all energy provided by the transmitter is transferred into electromagnetic energy and radiated out of the antenna.
Jim Abercrombie, in Understanding Antennas for the Non-Technical Ham, discusses two key concepts in effective antenna system design:
"For maxmimum power transfer from transmitter to the antenna, the antenna system must be resonant, and the resistance of the load (antenna system) has to be equal to the internal resistance of the source (transmitter)." (A "resonant" antenna system is one that allows maximum electromagnetic energy to be transferred at the frequency of the energy being transmitted. A term usually used for this frequency is "resonant frequency").
Regardless of the type of antenna, it must be designed so that all energy provided by the transmitter is transferred into electromagnetic energy and radiated out of the antenna.
Jim Abercrombie, in Understanding Antennas for the Non-Technical Ham, discusses two key concepts in effective antenna system design:
"For maxmimum power transfer from transmitter to the antenna, the antenna system must be resonant, and the resistance of the load (antenna system) has to be equal to the internal resistance of the source (transmitter)." (A "resonant" antenna system is one that allows maximum electromagnetic energy to be transferred at the frequency of the energy being transmitted. A term usually used for this frequency is "resonant frequency").