Indoor Vs. Outdoor Antennas
Indoor antennas are generally small, designed to be placed on or near your TV. Outdoor antennas tend to be significantly larger and are intended for roof- or attic-mounting. In general, the larger an antenna's surface area is, the stronger the signal it will provide. The relative strength of the signal an antenna can deliver to a tuner is referred to as "gain" and is measured in decibels (dB). The higher the dB rating, the greater the gain.
Nearly all outdoor antennas perform better than even the best indoor antennas. Along with their size disadvantage, indoor antennas have a height disadvantage, and are adversely affected by the walls of a house and even by movement of people in the room. Other sources of household interference include fluorescent lights, computers and cordless phones.
Compared to roof-mounting, installing an antenna in your home's attic has several appealing advantages: installation is much easier, the antenna is hidden from view, and the antenna and connections are not directly exposed to harsh weather.
The main disadvantage of attic-mounting is poorer reception. As an example, a single layer of asphalt shingles over a standard plywood roof creates a 30%-50% reduction in signal strength. Attic-mounting can be an effective option in areas where strong signals are present. To maintain adequate signal strength, an amplifier or preamp is often used.
Other potential obstacles to attic-mounting include a metal roof, aluminum siding, metal gutters, or foil-backed insulation in your walls or under the roof. Any of these conditions can result in signal interference or blockage.
