We bought a box, but it was a while later that we learned we needed a special antenna to go with it. We bought the one shown in the photo. It also comes with an active (powered by a voltage adapter) signal amplifier. This one is $37 at Amazon.com (plus shipping and handling). I must be slow mentally, because it took me a while to realize the Digital TV signal utilizes a basic UHF antenna.
We live 30 miles (48 km) from the local broadcast towers. An antenna like this should give us super fine reception. But, pointing it in the exact direction of the tower is critical. It does not function well without the signal amplifier, and the picture pixelates or goes to "No Signal" when someone walks across the signal path in another room. Mounting it in the attic might help, but one of our stations is located about 45 degrees clockwise from most of our stations.
For pennies I made a better antenna.
Step 1: Start Making the Antenna
Step 2: Mount the Aluminum Strips
Step 3: Attach Twin Lead
Step 4: Provide a Strain Relief
Step 5: Add a Support to the Furring Strip
Connect the 300 to 75 ohm transformer to the input on your converter box. Connect the converter box to the TV. Run a scan so the converter finds available stations. Experiment with the placement of the antenna for your best reception and enjoy. Also try placing your antenna so it is vertical rather than horizontal.
When I was finished, I found this cheap antenna performs better than the commercial antenna in the first panel of this Instructable. It is not as dependent on directional alignment and once properly aligned, no channels pixelate or fail with "No Signal." It did not lose a picture when someone walked across the signal path.
Step 6: Need Amplification?
Note: I have always wanted to try making the reflector from a wire screen. It should work, but it would need more support to hold its proper shape.
Step 7: What Is a Parabola and How Do I Make One?
The "B" lines are always perpendicular to the base line. The "A" lines change their angle in order to connect with the "B" lines. Use two yardsticks and a square. Plot points where the yardsticks cross over one another while the measurement shown on each yardstick is the same. The more points you plot, the more accurate your parabolic curve will be. If you are careful, you can plot only the left half of the curve and then flip it over to copy it onto the right half of the paper.
The end result is that any signal (TV, radio, sound, light) coming to the parabolic curve in parallel rays will be gathered in strength at the focal point and amplified because they are concentrated.