Television Antenna - Simple/indoor

Simple/indoor

Simple half-wave dipole antenna for VHF or UHF loop antennas that are made to be placed indoors are often used for television (and VHF radio); these are often called "rabbit ears" or "bunny aerials". because of their appearance. The length of the telescopic "ears" can be adjusted by the user, and should be about one half of the wavelength of the signal for the desired channel. These are not as efficient as an aerial rooftop antenna since they are less directional and not always adjusted to the proper length for the desired channel. Dipole antennas are bi-directional, that is, they receive evenly forward and backwards, and also cover a broader band than antennas with more elements. This makes them less efficient than antennas designed to maximize the signal from a narrower angle in one direction. Coupled with the poor placing, indoors and closer to the ground, they are much worse than multi-element rooftop antennas at receiving signals which are not very strong, although often adequate for nearby transmitters, in which case they may be adequate and cheap. These simple antennas are called set-top antennas because they were often placed on top of the television set or receiver.

The actual length of the ears is optimally about 91% of half the wavelength of the desired channel in free space. Quarter-wave television antennas are also used. These use a single element, and use the earth as a ground plane; therefore, no ground is required in the feed line. See also: Dipole antenna#Quarter-wave antenna

Soon after television broadcasting switched from analog to digital broadcasting, indoor antennas have evolved beyond the traditional "rabbit ears." RCA is one manufacturer which has commercially sold a Flat antenna. Flat Antennas are very lightweight. They are very thin, and square-shaped like a thin notebook. They connect to televisions, or to digital converter boxes with a single coaxial cable. Flat antennas are sold with an optional signal amplifier. The Amplifier must be plugged into a power source, but the flat antenna does not require a power source. The flat antenna may need some moving around, to achieve an optimum reception, but it eliminates a lot of manual manipulation which is inherent in use of the "Rabbit ears."