While flat antennas can receive a signal from farther away than omnidirectional antennas, they do need to be more carefully aimed in order to receive a good signal from the broadcasters. Flat antennas work well when most or all of the television stations in an area come from the same direction.
Most flat antennas can receive signals from about a 30 to 50 degree range. That means that the broadcasting stations need to all be in roughly the same direction for the antenna to work without repositioning for different stations. If you have a compass -- or compass app on your smartphone -- you can see the degrees marked out. Line up the compass with the middle of the antenna and count 15 degrees on either side of the middle. That gives you the range of reception that you're likely to get with your antenna.
Finding the Stations
The FCC maintains a list of DTV broadcasters and a mapping tool to help you find the stations closest to you (see link in Resources). Enter your address to see the different stations within range of you and the strength of their signals. If you click on the name of a station, you will get more details including the compass direction from your location to that station's broadcast tower. Note the compass degree for each station you want to receive with your flat antenna. Count the number of degrees between the stations that are farthest apart, and remember that 0 and 360 degrees are both due north, so if one station is at 359 and another is at 29, they are only 30 degrees apart.
Aiming Your Antenna
Pick the point between your two most distant stations and aim your antenna toward that point as a start. Flat antennas should be aimed so the flat surface is perpendicular to the signal. If you have broadcasters at 183 and 192 degrees, take the average of the two and aim your antenna at 187.5 degrees using a compass or compass app on a smartphone. Of course the TV signals bounce off of all sorts of objects -- especially metal -- so you will need to fine tune your aiming by looking at the actual signals. Switch between the two stations that are the farthest apart and adjust your antenna so they both have equally clear signals.
Antennas are like Goldilocks; they need things to be just right. If the signal is too strong they won't work well, or if it's too weak they won't show you a picture -- but if you get things just right, it will be grand. If the transmitter is within only 10 or 20 miles from you, you might be getting a signal that's too strong. You can add an attenuator to reduce the strength and keep your TV tuner from overloading. If you have more than about 50 miles between you and your TV tower, you might need a pre-amp to add some power to the signal so your tuner can make it out. Typically, flat antennas work best with strong signals coming from generally the same direction.
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