A parabolic antenna is an antenna that uses a dish that is shaped like a shallow bowl. These are used for satellite television, radio, astronomy, cellular telecommunications, and radar. They can also be used to boost the signal of a wireless Internet router. Parabolic antennas are also known as dish antennas.
The first parabolic antenna was created by Heinrich Hertz in the late 1880s. His early design was created using a brass sphere, zinc sheet metal, and wood. Hertz used one antenna for transmitting signals and another for receiving signals.
Hertz used his antenna to help prove the existence of electromagnetic waves. As a result of this and other accomplishments, his name is now the term used for radio and electrical frequency measurements. These include hertz (Hz), kilohertz (kHz) and megahertz (MHz).
Today’s antenna designs improve upon Hertz’s early work. A single antenna can transmit and receive signals. A parabolic antenna is a unidirectional antenna since it transmits signals in only one direction. The dish part of one is known as the reflector.
The reflector creates a large surface area that the antenna uses to receive and transmit signals. The innermost part of the dish is the vertex. The reflector gathers and strengthens the signals it collects. This strengthening of the signal is called gain.
The strengthened signal is aimed at the transmitting and receiving element at the focal point, or focus, of the parabolic antenna. The focal point is usually directly opposite the bottom of the dish. The element, or feed, sends signals to and from the appliance receiving the signal, such as a television receiver or radio.
The distance between the focal point and the vertex is called the focal length. For a parabolic antenna to work properly, the focal length must be correct. It is based on the diameter of the dish. To calculate the focal length, the reflector diameter is squared, and then divided by 16 times the depth of the reflector. The result is the correct distance to use between the focal point and the vertex.
Parabolic antennas are usually mounted on a roof, the side of the building, or on a stand outdoors. They can also be placed indoors when used with Internet routers. The device must be aimed in the correct direction to collect the signal. Usually, the appliance connected to the antenna will indicate the antenna signal strength. This helps the user better aim the antenna to get a stronger signal.
