Building an OTA HDTV Antenna

Screws and Washers holding coat hanger parts to the board
This week I built a TV antenna. Previously, we had been using a commercially purchased Radio Shack antenna with a built in pre-amplifier, but we left it mounted on the (tall, exterior) wall of our previous house. We had planned on purchasing a new antenna to place in our attic when I found plans on the Internet for how to make your own out of coat hangers and scrap wood. (Really, what CAN’T you find plans for on the Internet?)

Located in Metro Atlanta, I am lucky to be able to pick up quite a few HDTV stations using the small Radio Shack antenna.
My home-built antenna is larger and less aesthetically pleasing, but it does have the benefit of not needing a power injector (for the pre-amplifier) and pulling in some stations that we couldn’t receive before. Plus, it cost $2.92 for a 300 to 75 ohm transformer that I bought with a pair of rabbit ears at a thrift shop, plus a lot of scrap parts I found in the garage and my wife’s closet. (If I do all the laundry she runs out of coat hangers…)

The coat hanger wires all cut and laid out.
I cut the metal coat hangers into V’s where the leg of each V is 8″ long and bent them so that the tips of the V’s are 3″ apart. Horizontally, the points of the V’s are separated by 2″. Vertically, each V is mounted 5 and 3/4″ apart. Then I sanded the enamel off of the steel at the connection points so that they would make electrical contact and just screwed them down with big washers. (I tested with a multi-meter, zero ohms at each connection!) I used heat shrink tubing to insulate the upright wire rails from each other when they crossed. The only places I soldered were to connect wires from the center rails to the matching transformer (mounted on the back of the board).
75 to 300 ohm Transformer

Because my “in-stock” wood screws were too long, they stuck out of the back of the board. I eventually used the top two to affix the antenna to a rafter in the attic, so they serve double duty.
antenna screwed to rafter in attic

I was more than happy with the signal quality of this home-built antenna. It easily rivaled my previous small radio shack patch antenna. In addition to the channels I could previously receive, I can now pick up the following additional stations reliably:

  • 8 (8.1 GPB) 21kW transmitter from Stone Mountain
  • 29 (32.x) APGuide/Prism/ThisTV (15kW from Druid Hills site)
  • 35 (53.1) WDTA (1.5kW from the Sun Trust Plaza)
  • 40 (40.1 WIRE) (15kW from WUPA Tower)

I found the instructions for this antenna on the Make Blog. I was not impressed with the details of the instructions. They gave a good overview, but some of the measurements and directions were lacking. They say that their wooden board is 3″x20″, and that the holes are 1/2″ in from the outside, but did not actually specify an internal dimension between the two columns of holes. I decided this meant that the holes should be 2″ apart. (My board was not 3″ wide). They also had a random 2″ mark which I interpreted to mean that the top holes started 2″ from the top of the board, and thereafter the sets of holes were to be 5 and 3/4″ apart. They had a 10″ mark to the “center” of the antenna for mounting the wires for the 300 to 75 ohm antenna, but according to my math (2″ + 5 3/4″= 7.75″) and (7.75 – 10 = 2.25, not 2.875) that isn’t quite the center distance between a set of holes…. I just went for the center distance because the text said to mount it in the center.

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