Make This Powerful HDTV Antenna Out of Cardboard
Keep reading. You're about to discover just about the most unlikely thing you could ever expect to make out of cardboard.
As a high-definition TV owner, you're looking for the easiest and least expensive way to get your local network channels. You may have realized that this is something you don't have to pay your cable TV provider for. Crisp, clear, digital, high-definition signals are available for free from your local TV stations: All you need is the right antenna.
But HDTV antennas can be expensive: $40 to $70 for a good indoor model. This is one of the best HDTV antenna designs ever, and also the least expensive, because you will make it yourself using cardboard and foil.
Here's a secret you won't hear from an antenna manufacturer: The TV signals themselves don't care what the antenna is made from, as long as the correct arrangement of electrical conductors is present. With this antenna, that's aluminum foil. As outrageous as it may sound, this antenna can be just as effective and powerful—or more so—as any other antenna, no matter the cost or construction.
I have taken some of the best antenna designs I could find and modified, experimented, built, and rebuilt them until I had the best performing HDTV antenna I have ever tested. They just happen to be made out of cardboard.
Print and Cut Out This Pattern First
- Dual-Bowtie HDTV Antenna Paper Pattern
Click the above link to open your pattern in Adobe reader. You will need legal size paper (8 1/2 by 14 inches) to print these correctly.
What You'll Need
Don't let the simplicity fool you. This is a powerful antenna that easily beats a $50 HDTV antenna. Refer to the yellow diagram below to familiarize yourself with the parts. You can build it in just 13 steps.
- Scissors and a pen knife/boxcutter.
- Felt pen.
- Ruler or tape measure.
- Stapler or nuts/bolts (see directions below).
- About three square feet of cardboard or Foamcor. The longest dimension is 14 inches. (I'm using cardboard from an old computer box for my example.)
- Aluminum foil.
- Cable, either 75-ohm coaxial or 300-ohm twin-lead.
- A balun.
What's a Balun?
To connect the antenna to your receiver you will need some wire and an adapter called a balun (the word means balanced-to-unbalanced). For HDTV, your receiver almost certainly has a 75-ohm unbalanced connection. Antennas, including this design, are usually 300 ohms balanced. So there are two approaches to achieving the right type of connection, and two types of balun:
- The first way is to connect a 300-ohm twin-lead wire (flat wire) to the antenna and add a balun at the end of the wire that connects to your TV.
- The second way is to connect the balun directly to the antenna and run 75-ohm coax (round wire) from the antenna to the TV. Both approaches work fine.
You can find antenna baluns (also called TV-matching transformers) and wire at places like Home Depot, Radio Shack, eBay auctions, and even department stores.
Building the Dual Bowtie Indoor HDTV Antenna
- Choose good sturdy cardboard or other material. Cardboard is actually one of the best choices for antennas because it is very light and will offer virtually no interference with the passage of the TV signal. Corrugated cardboard is great (it's very airy) and Foamcor is a good choice, too (it's very sturdy and attractive.) You can find Foamcor in lots of different colors at your local office supply store. Corrugated cardboard is not as pretty, but it can be dressed up with paint, felt markers, or construction paper. Plastic should also work fine, though I haven't done specific testing. I don't recommend wood (unless very thin) since it will impede the TV signal slightly.
- Any glue that works on wood and paper, like Gorilla Glue or Elmer's wood glue, should be fine.
- Any aluminum foil will work but you'll find it easier to work with thick, heavy-duty foil.
- Be creative with the construction if you want to but you must pay attention to the placement and spacing of the foil, since this is what does the work of receiving the TV signal. Every other part of the design can be expanded, contracted, colored, decorated, or augmented (with non-conductive materials) to customize the antennas to your surroundings.
- If you want to use one of these antennas outside, use sturdier metal. Home improvement stores sell sheet aluminum that is light enough to cut with shears or tin snips. The bowties and reflector (backing) on the bowtie antenna should ideally be made of a porous metallic material like window screen, chicken wire, or pulled metal so it won't catch the wind.
Step One: Cut Out the Pattern
- Locate the patterns for the dual-bowtie antenna (using the above link), print and cut them out as directed. You should have patterns for the cardboard bowtie "wings," the foil bowtie "wings," support bracket, foot, and a stencil for cutting openings into the reflector (the backing).
Step Two: Cut Out the Reflector
- Cut the reflector panel out of a sheet of cardboard. There is no pattern for this. Just cut a 13"x14" piece of cardboard or Foamcor. If you wish to paint it or glue construction paper to the front, you may do so now. Turn it over, apply a little glue, and attach aluminum foil to cover the entire backside.
Step Three: Mark Bracket Placement
- Position the reflector so that the long dimension (14 inches) runs away from you and the shorter 13-inch dimension runs right to left. This means the bottom edge of the antenna is now closest to you. Using a ruler, find the exact center of the bottom edge and place the stencil (sheet C) along the bottom edge of the reflector so the little "V" arrow points to the center.
- Use a piece or two of tape to secure the stencil sheet in place. With your felt tip marker, mark the slots where the feet will go and trace the inside of the two rectangles where the support brackets will mount.
- If you plan to use the feet (as opposed to hanging the antenna), go ahead and cut out the foot slots you just marked. Keep the thickness of your cardboard in mind when cutting out these slots. You want the feet to be a tight fit. It's OK to cut these slots a little too skinny, as you can always enlarge them later if you have to.
Step Four: Cut Out the Rectangles
- Using your pen knife or boxcutter, cut through three sides of the two rectangles you traced onto the reflector.
- If you remember from the stencil, the bottom edges of those rectangles were marked with dotted lines. Those are folds, not cuts. If your cardboard or Foamcor is hard to fold, you may make a light score with your knife on the dotted line to make it easier to fold.
- These flaps of cardboard will lean out towards the front and act as a brace for the support brackets. When cutting out the slots where the feet will fit, try to adjust the width of the slots for the material you are using. We want this to be a tight fit, so try to err on the side of making the slots too small. They can always be enlarged later.
Step Five: Cut Out Other Cardboard
- Cut out your other cardboard pieces. Use a small piece of tape to hold the forms in place while you trace around them on your board. You will need two cardboard "wing sets," two support brackets, and two feet.
- After tracing, cut the patterns out of the cardboard, cutting around the INSIDE of the lines (since you traced the OUTSIDE of the patterns, the correct dimensions are on the inside).
Step Six: Cut Out the Brackets
- If you want to paint or color any of these parts, you many do so now (I'm using a felt pen). When cutting out the brackets, first do the whole square shape, and then cut out the small slots afterward (I like to cut two sides of the little slots with scissors, then cut the third inside edge with a knife).
- Try to adjust the width of the slots in the brackets for the thickness of the material you are using. We want this to be a tight fit, so try to err on the side of making the slots too skinny. They can always be enlarged later.
Step Seven: Trace the Foil Wings
- Cut out the foil "wings" using the foil pattern. You need two of these. Use a small bit of tape or two to hold the form in place while you trace around them onto the foil with your felt marker.
- Foil may not cut well with a pen knife or boxcutter. The scissors may work best. Try both. You will still need your pen knife for the smallest inside cuts, so work carefully. It is very easy to damage the foil while cutting. If it tears, trace the pattern again and start over.
Step Eight: Mark the Folds
- If you look at the cardboard wings pattern, you will see dotted lines where the folds go. Use your pattern to mark the correct place for these folds on the back of your wings. You'll have the best results making clean folds if you make light cuts (scores) along these lines. Then fold forward (away from the cut), opening up these light cuts.
Step Nine: Secure the Folds
- The halves of each wing should make an angle of approximately 90 degrees to each other. It may spring back, so adjust these folds until they appear to be staying in the right position. Once you are satisfied, put a bead of glue into the scores. This will help hold the position of the folds.
Step Ten: Glue the Cardboard to the Foil
- Spread a light coat of glue over the rest of the wing backs and down the connecting struts. Glue only goes on the inside half of the struts, not on the edge where the slots are. Carefully fit the foil wings on top of the glue, position, and smooth. The foil connector that goes down the strut does not cover the slots. Repeat for the other set of wings.
Step Eleven: Insert Brackets into Holes and Fit Feet, if Needed
- Place a cardboard bracket into each of the rectangular holes on the front of the reflector. To accomplish this, pull the flap forward from the hole, fit the bracket in, and twist it into place so the slots on the bracket engage the edges of the hole. When you let go of the flap, it should support the bracket. Move this flap and find the point where the bracket extends straight out from the reflector, then place a piece of tape to hold the flap and bracket together. You will glue these spots later, when all of the parts are assembled.
Step Twelve: Mount the Wings to the Brackets
- Mount the wings to the brackets by matching up the slots on the wings to the ones on the brackets. If everything fits, apply a dab of glue and fit the wings in place. Use a twist-tie or some string to hold the wings in place while the glue dries. Also, pay attention to the position of the wings relative to the reflector. Each wing should stand straight out and not sag toward the reflector. If necessary, fit a temporary piece of cardboard between the wings and the reflector to hold them in the right place while the glue dries. The distance between the back of a wing and the back of the antenna (the distance from foil to foil) should be 3 1/2 inches.
- While you're at it, make sure that all parts fit well and that the antenna sits square and true. Now is a good time to glue the back end of the brackets to the reflector as well.
Step 13: Connect the Wiring to the Antenna
- Come back when the glue is dry and connect the wiring to the antenna. If connecting twin-lead, separate the wires and strip about 3/4" of the insulation off. Then staple the exposed part of the wires to the exact center of the struts between the wings. If connecting the balun directly to the antenna, either staple the wires or drill or punch a small hole and install a small screw, washers, and a bolt to the exact center of the strut between the wings. Carefully connect the wires from the balun to the screws. (The drawback of screws is that they can never be tightened down hard onto cardboard.)
- Experiment with the placement and rotation of your antenna until you find a good orientation. Generally, the broad front of the antenna (the bow ties) should be pointed toward the TV station you want to receive.
Usage and Placement
The majority of HDTV broadcasts take place in the UHF TV band, so this antenna has been optimized for these frequencies.
The placement of your antenna is key. The dual-bowtie antenna can be hung on a wall, but it really needs to be pointed toward the broadcasting TV towers. You will almost certainly have to experiment with placement and rotation until you find the spot where your receiver registers a good signal.
In some cases, especially if you are in a home with aluminum siding, you may not be able to acquire an adequate signal indoors. In this case, you still have a couple of options.
- The first is to place the antenna in your attic, above the influence of your aluminum siding, and run a cable down to your set.
- The second is to hang the antenna out of a window. In general, this is not something you want to do with a cardboard antenna, but if you add some extra cardboard bracing, enclose the antenna in a plastic bag, and devise a sturdy mount. The antenna will be able to survive this way for quite a while, and if the next hurricane blows it away, what have you lost? Just a few cents worth of materials!
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