How To Compare Exterior Antennas for DTVby David Lipscomb
The allure of a new high definition television increases once you realize digital programming is freely available over the air. Terrestrial HD reception is the best-looking digital content available, without recurring monthly charges. Rooftop or attic antennas pull in this content, broadcast from local towers in your area. Additionally, the Telecommunications Act of 1996 authorizes mounting this antenna to your home or condominium for the best reception without interference from local homeowner's association. Although there is a wide variety of antenna types, resources like AntennaWeb.org help you choose the exterior DTV antenna most suited to your location.
Local broadcasters in most urban areas place their antennas relatively close to one another, usually within a 20 degree radius. Inevitably, there will be one or two rogue towers that you want to receive programming from, isolated from the rest. The location of these towers will influence your choice of antenna. Directional or uni-directional antennas are generally more powerful, larger arrays designed for maximum reception within a narrow field. This means that increased signal strength from the antenna to the tuner, with few if any dropouts. You can place this antenna on a rotor to maximize signal for any tower you target. The easier but less powerful method is to deploy an omni-directional antenna, pulling in signals all around you. Remember that the further you are from broadcasters, the more a directional antenna can do for you. In most cases, fringe areas are considered between 50 and 75 miles from local broadcasting towers.
Where Are the Towers?
Understanding different antenna types is useful once you plug your data into AntennaWeb. When you enter your address and approximate installed antenna elevation, AntennaWeb calculates your distance and location relative to broadcasters. The site then assigns antenna options based on this data, using a specialized color coding system. Matching this color to the color on an antenna package at retail is how you make your purchase based on AntennaWeb's recommendations. Although the site helps you choose the antenna, it's still important to install the unit away from aluminum siding, large trees and adjacent structures. Failing to do so induces multipath, a condition where the broadcast signal reflects off of multiple objects, hitting the antenna at different intervals. These different arrival times cause cancellation, reducing signal strength.
You might have an aesthetic concern with a large aluminum antenna on your rooftop. There are two primary ways of approaching this. The first is to find the largest antenna you can fit into your attic while following AntennaWeb's recommendations, mounting it to a rafter or in a concrete-filled bucket. Signals punch through wood and vinyl siding without much difficulty, but metal siding will block the signal to a large degree. You can also mount a smaller square or round antenna to the side of your house, using a mount resembling the type a small satellite dash would use. These are surprisingly powerful, but slightly more directional, making them more finicky in terms of aiming. Such antennas are usually amplified designs, necessary in mitigating the smaller receiving area used by these arrays.
Mounting an antenna in a fringe location or using a coaxial cable run in excess of 100 feet makes an antenna preamplifier and amplifier necessary. Preamplifiers mount to the mast of the antenna near the array, boosting whatever signal is present. At the other end and installed in a basement or access room is the amplifier, compensating for these small signal strength losses and sending the signal on its way. Amplifiers are especially useful when splitting the antenna feed multiple times, since each split would otherwise result in a 3 decibel loss per division. For this reason, the majority of coaxial distribution panels are amplified, with some offering individual controls to boost or attenuate the feed based on the panel's proximity to each television tuner. This is necessary since too much signal overdrives tuners, resulting in a bright white or washed out image, hardware damage or both.
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