User:B137/Television antenna
A television antenna is an antenna specifically desigend for the reception of over the air broadcast television signals, which range from 54 to 806 MegaHertz, which lies in the VHF to UHF spectrum. To cover this range; they generally consist of multiple conductors of different lengths which correspond to the wavelength it is intended to receieve. The length of the elements of a TV antenna are usually half or one quarter of the wavelength; the wavelength equals 300 divided by the frequency. [1] The actuall design of a multiband United States television broadcast reception antenna has not changed since the switch to digital television in February 2009. [2]
Simple/indoor[edit]
Many antennas used for television are a simple quarter-wave dipole antenna with one or a few loop antennas; often these are refered to as "rabbit ears". The length of the "ears" is usually one quarter of the wavelength of the received signal, which is not as efficent as a design where the elements are one half; as is common with large rooftop or aerial antennas. [3] On the horizontal plane, dipole antennas are all-directional. That is, they transmit evenly in all directions and display and even gain from all directions.
Aerial/outdoor[edit]
An aerial or rooftop antenna generally consists of multiple conductive elements that are arranged such that it is a directional antenna. The length of the elements is usually one half of the signal wavelength; rendering increased efficiency over a one quarter wavelength design. The longer elements for picking up VHF frequencies are in the "back" of the antenna, relative to the devices directionality, and the much shorter; UHF elements are in the "front", and the antenna works best when "pointing" to the source of the signal to be received.
The smallest elements in this design, located in the "front", are UHF director elements, which are ususally identical and give the antenna it's directionality, as well as improving gain. The longest elements, located in the "back" of the antenna form a VHF phased array. Other long elements may be UHF reflector [4]
Another common aerial antenna element is the corner reflector.