Ideally an antenna should be mounted at the point where the signals are the strongest, though often this is impractical or impossible. The antenna should also be mounted where it can be easily serviced should repairs or adjustments be required in the future. There are many acceptable locations where an antenna can be mounted such as on your roof, in your attic, on a wall, on the eave of your house and even on the ground. Having a clear line of sight is the most important consideration but carefully aiming(orienting) the antenna, and adjusting its height often can overcome the problems created by installing it in a slightly weaker signal area.
In an area where there is a relatively short, unobstructed signal path between the installation and the transmitting towers you can mount the antenna just about anywhere and receive sufficient signal. As you move deeper into the fringe areas however, there may be significant differences in signal strength at various points around your home. This is where careful antenna selection, precise orienting, and accurate adjustment of the height becomes a little more important. Typically you should be able to locate a spot where there is both a usable signal and easy access to the antenna. Large trees, tall buildings and obstructions can present reception problems. Nearby high-voltage power lines can also cause interference that cannot be completely eliminated. Consequently, the further the antenna is from large trees, buildings, obstructions and high-voltage lines the better the reception will be.
To begin the process of determining the best location for an antenna, go to www.antennaweb.org to determine the expected signal strength of the channels you would like to watch. If the channels you want to watch are all in the Yellow category, an indoor antenna should be sufficient to pick up those channels. If the stations are in the Green category, an indoor antenna may work, but an attic mounted antenna may be a better choice. If your desired channels are in the Red category, an attic mounted antenna may work, but a small outside antenna would be recommended. If the stations you want to watch are in the Blue or Purple categories, a larger outdoor antenna is the best choice. Each of these antennas will have different mounting requirements.
The height at which the antenna is mounted can also be critical, especially in areas where larger outdoor antennas are required. A few feet up or down may make a big difference in the level of the received signal(s), especially on UHF channels. The best way to determine the height requirement is to use a test antenna and a field-strength meter, and measure received signal strength at different heights with the test antenna oriented towards the desired channels. If a field strength meter is not available, a small portable TV can be used with a simple dipole antenna (CM-4001HDBW). Simply raise and lower the antenna until the best picture is received.
The height at which you ultimately mount the antenna depends on two things, signal strength and practicality. You should mount the antenna only as high as necessary, even if your meter indicates that the signal level continues to increase as you raise the antenna. Choose the height at which you get the highest signal level without having to resort to a guyed mast or other more expensive and difficult to install equipment. Your objective should be to get as close as possible to an unobstructed line of sight between the transmitter tower(s) and the receiving antenna so that the signal clears all large buildings and other obstructions.