A television, be it a conventional CRT or a recent plasma or LCD flat screen, has a tuner of some sort that receives the channel information. If no antenna nor cable is connected, the only means to provide that incoming channel feed is with a satellite dish. There are do-it-yourself satellite dish projects on the web as there are antenna projects that can allow for free reception of HDTV signals. Television without an incoming receiver of some sort? No, but there's a proven way to get it for free.
Obtain a piece of plywood, panelling, heavy cardboard or anything else that provides a rigid surface. This backing should be approximately 30 inches by 16 inches, enough to extend to the edges of the coat hanger array. If your HD antenna is going outside, metal drying racks from a dollar store or grates from an old oven also work.
Wrap the board with aluminium foil. Secure it with high-temperature duct tape on its backside if the antenna will be in an attic or outside.
Cut a 2-by-4 for outside or a 1-by-4 for inside to 41 inches in length. This length affords enough room to make the antenna to attach a motor if you care to make the antenna movable.
Place the 2-by-4 narrow side down on your work surface or floor. Place the backing board with the aluminium face down on top of it. Center the aluminium board. Nail or screw it in place.
Measure the hanger attachments 7 inches from one another on both edges of the board. The matching transformer, also known as "balun," is attached between “bow ties” No. 1 and No. 2.
Attach the screws with washers, making sure the washers do not touch. Drive the screws in halfway. If you're using the 1-by-4 for inside use, place the screws on the wide portion of the board, rather than on the narrow side as on the 2-by-4.
Cut the "hook" off the coat hangers and the curly part of the opposite end. Straighten each hanger and fold it in half, so a V is formed in the middle. Trim each hanger so that each V has 7-inch legs. You will have eight hanger Vs. Sand or scrape any paint or insulation of the hanger Vs, so that bare wire contacts each washer.
Secure each of the V hangers under the screws and washers. You can also use any 12-gauge bare wire, if you prefer.
Run the two remaining hangers or other solid wire from each top “bow tie” and down the opposite side through the third bow tie, making the final connection on the fourth bow tie on the same side as the first connection. The wires will cross between the first-second and third-fourth bow ties, and at these crossing points, at least one wire should be insulated.
Attach the UHF/VHF transformer/balun. This is the connection for the cable that goes to the TV. Use the marks between hanger bow ties No. 2 and No. 3 where previously marked.
Recheck that your V wires are the same length and parallel with the foil backing (ground or wall if you're not using the background.) Make sure the spread of all Vs is uniform and parallel with the foil background.
Connect this homemade HD antenna to your television and get HD reception for free.
Total construction time is 30 minutes to 1 hour. "Balun" is a contraction of "balanced" and "unbalanced." It electrically isolates the antenna from the coaxial cable. Balun is also known as a UHF/VHF transformer. It is the means to connect the cable from the antenna to the television.