An outdoor TV aerial is a high-gain directional antenna often needed to achieve adequate reception in fringe reception areas around Cardiff, greater than 15 miles from the television station. Outdoor aerials have a unidirectional radiation pattern so the correct end of the aerial must be pointed at the TV station. The received television signal passes down a feed line (transmission line) into the house to the television. Older aerials used flat 300 ohm twin-lead cable. This had to be kept several inches away from metal objects such as the antenna tower or gutters, so it had to be mounted on standoff insulators. Modern aerials in Cardiff use 75 ohm RG-6 coaxial cable which attaches to the television with a type F connector.
Outdoor aerial designs are often based on the Yagi-Uda antenna or log-periodic dipole array (LPDA). These are composed of multiple half-wave dipole elements, consisting of metal rods approximately half of the wavelength of the television signal, mounted in a line on a support boom. These act as resonators; the electric field of the incoming radio wave pushes the electrons in the rods back and forth, creating standing waves of oscillating voltage in the rods. The aerial can have a smaller or larger number of rod elements; in general the more elements the higher the gain. Another design, used mainly for UHF reception, is the reflective array antenna, consisting of a vertical metal screen with multiple dipole elements mounted in front of it.
If you're looking for a reliable TV installation service company in the Cardiff area, contact me for free advice & a quotation.
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