Making a homemade high-power HDTV antenna is a matter of enhancing the incoming over-the-air signals: mount the antenna outside, use a backing reflector with the antenna, position the antenna more precisely and/or add a preamp to the antenna to boost the signals before they reach the TV. Finally, use the bow tie antenna that replicates a DB4 antenna, as that brings in the full spectrum of VHF and UHF channels (2 through 65).
From Wire Hangers to HDTV
The keys to make a great high-power HDTV antenna hanging in a closet. Begin, however, with a 41-inch length of 2x4. Add a total of 10 wire coat hangers from the closet or laundry, eight for "V"s that together make the bow ties, and two more to interconnect them. Get wood screws and washers to secure each hanger segment, and a VHF/UHF from a dollar store.
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Old metal shelving or oven grates make an excellent backing element, because they offer little wind resistance and approximate the backing of manufactured DB4 antennas. However, a 30x16-inch piece of plywood or heavy cardboard covered with aluminum foil is the prototypical DIY backing reflector, although it is better for the attic because it's a solid surface.
Assembly
Attach the backing reflector to one narrow side of the 2x4 with nails or screws. Then, attach each V section hanger to the opposite edge of the 2x4, four to a side, five inches from the top, and seven inches between each hanger. Repeat the sequence on the other side at exactly the same measurements, making sure the washers don't touch one another.
Two additional 24-25 inch hanger lengths connect all the "V"s. Connect one from the top left "V" position, cross it over to right #2, continue down through right #3 and end at left #4. Repeat the sequence, starting at top right, with the second hanger length. Once they're both secured beneath the washers, and both of the two crossing points are insulated to prevent shorting, attach the two wire leads of the VHF/UHF adapter the two interconnecting hanger lengths, halfway between bow tie pairs 2 and 3.
Positioning and Boosting Tips
The bottom of the 2x4 can be installed in a motorized base if remote control positioning of the antenna is desired. Cut the bottom of the 2x4 narrow enough to put it into a motorized base if remote control positioning of the antenna is desired. Otherwise, mount the antenna in an attic or outside, position it for maximum signal strength, and free HDTV over-the-air channels are yours.
Remote areas far from transmitters can benefit from a preamp to boost the signal from the antenna to the television can provide a further signal boost.