Indoors Fractal HDTV Antenna





Introduction: Indoors Fractal HDTV Antenna

This antenna design grew out of my attempts to build an indoor HDTV antenna using fractal patterns after  I had watched a TV show and had read a magazine article on the use of fractal patterns in cell phone antennas,  My goal was to design an antenna that not only worked well, but one that was easy to build and could be built from easiliy obtainable materials.

The result is an antenna that is somewhat omnidirectional,  and performs well receiving digital TV signals at my home from the low end of the VHF high-band (i.e Channel 7 at 174 MHZ) to the high end of the 600 MHz UHF band. (There are no channels in the 700 MHz band in my area, but Channel 51 at 692 MHz is one of the strongest signals here.)

This antenna can be used at a maximum line-of-site distance from the broadcast tower of about 50 miles for high power stations, and somewhat less for low power stations.  I'm sorry that I can't be more definite about these distances, but a lot depends upon the type of construction used in the building and the location of the antenna within the building (e.g. downstairs living room vs. second story bedroom or attic).  

So, with all that in mind, let's get started. 

Step 1: Gather Needed Materials

The materials you will need are:
  1. A 150mm X 400 mm ( 6 inch X 15 3/4 inch) piece of poster board.  This is the stuff from which cake boxes and the gift boxes for shirts and blouses are made.  A 24 inch X 28 inch sheet of it can be bought at hobby stores and other places for less than a dollar.
  2. The pattern for the antenna.  Download the PDF file at the bottom of this page.
  3. Some cellophane tape.
  4. Scissors.
  5. Map pin or other sharp pointy object for punching holes in poster board.
  6. 3.2 meters (~10.5 feet) of small diameter (24 - 20 AWG) copper or aluminum wire.   This can be salavaged from an old discarded electric motor or purchased from a hobby or hardware store.
  7. Crimp connectors and crimping tool or a soldering iron and solder for connecting lead-in wire to antenna.
  8. A length (let your situation be your guide as to the length) of 300 Ohm twin lead antenna lead-in wire and a 300 Ohm to 75 Ohm matching transformer.  The matching transformer can be purchased from Radio Shack, Wal-Mart, Target, on-line, or at any number of hardware stores.  Best prices are found on-line, you just have to wait a few days for delivery. 
  9. A length of 75 Ohm coax and a in-line 300 Ohm to 75 Ohm matching transformer can be used instead of the 300 Ohm twin lead antenna wire listed above as Item 8.  It's getting harder to find the good old fashion 300 Ohm twin lead antenna wire, and all the TVs manufactured in recent times have antenna connections for 75 Ohm coaxial cable.
  10. A craft knife or other knife with a small sharp blade for cutting Slots A & B in antenna form.

Step 2: Print Pattern and Prepare Antenna Form

The PDF file consists of two standard Letter Size (81/2 X 11) pages that should be printed at 100%.  The dimensions on the pattern are in millimeters and can be checked with a ruler to insure that your printer is set to print at 100%. 

When you have a printed copy of both pages:
  1. Cut the trailing end off of the first sheet.
  2. Lay the first sheet on top of the second sheet and align the pattern and big "plus sign" registration marks on top of each other.
  3. Tape the two sheets together.
  4. Use the scissors to trim the excess paper from the edges of the pattern leaving only a 150 mm X 400 mm rectangle.
  5. Tape the pattern to a piece of poster board and trim the poster board along the edges of the pattern.
  6. Tape the pattern to the poster board, use a couple of layers of shipping carton card board as padding, and use the map pin or other sharp pointy tool to punch hole at every point in the pattern marked with a dot.
  7. Use a craft knife or other small sharp blade to cut Slots A & B into the poster board.

Step 3: "Lace" the Wire Onto Antenna Form

Use a 1.6 meter length of wire for each side of the antenna form, and starting at the hole marked "Start" lace the wire back and forth from one side of the poster board to the other following the pattern.  Keep the wire as straight as possible between the holes and be careful to not kink the wire when pulling it through the holes.  Leave about 1/2 inch of wire on the back side of the poster board at the end of each wire to be used for connecting the lead-in wire.

The best way to connect the lead-in wire or in-line matching transformer to the antenna is to twist together the stripped wires of the lead-in/matching transformer with the end wires of the antenna and solder both connections.  If you don't have a soldering iron and solder, the next best connection is made using crimp connectors and a crimping tool or pliers.

After the lead-in/matching transformer is connected to the antenna, it's a good idea to punch a hole through the poster board on both sides of the lead-in wire or in-line matching transformer and tie the wire to the poster board using a small cable tie or tristy from a loaf of bread.

Step 4: Finishing Up

After the lead-in has been connected to the antenna, all that is left to do is to form the antenna into a cyclindical shape and insert Tabs A & B into Slots A & B.  (A little cellophane tape along the seam works wonders in maintaining the shape of the antenna.)

The antenna is now ready to be connected to the "Antenna In" connector on your TV or converter box.  The antenna works best if set on a window sill or taped to a window pane, but you should experiment with the placement and orientation of the antenna to find what works best for you.

Step 5: Adding a Decorative Touch

The antenna will fit into various empty clear plastic containers and can be used to display family photos or sports pictures.

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29 Discussions

Tigers; just made it last night, was using some 20g copper wire (2.35$ and a 2$ \RCA transformer). To say wow just isn't enough - it's amazing - the clarity of reception. although I think I may have struck upon one of your cardinal warnings - twisting/kinking the wire, in a few places on the build. am trying to see where it fits best to get some more free Digital signals (which actually are coming in better than the regular cable pic. Apologies in advance for the newbie question but using something like TV Fool to see what I should be able get- good? bad?

Will try another build- using same 20g, but being more patient and not twist/kink, etc.

And now to read the rest of these. Thanks again.



1 year ago

now I make again no work again with pantoon wire

I built this antenna and I am surprised by the reception. I can't catch anything without it being near a window, but we only have one local channel and we are 50+ miles from New Orleans, LA where all of our channels are located. I tried it in different direction facing windows and caught 23 super clear channels in one at a height of 5ft.

I would like to try a weather proof version which I can hang outside with a cable ground block going to a grounding rod or tying in to the house electrical ground. I am thinking about a waterproofing spray such as Flex Seal on the antenna. Does anyone have experience to share about converting this antenna to exterior use? Would a spray on sealer affect reception?


2 years ago

I made this today and right off the bat, with just a 6' piece of coax I picked up 4 channels which isn't bad for the rurals where I live. I'm in a low spot, but I have a line-of-sight view of both towers located at about 3.5 miles and 15 miles away. I need to get an antenna outside and see what I can pull in, but for now, this will get me some television. Thanks!

The pattern was kind of rough, didn't scale properly and didn't align, and I have access to design software, so I remade the pattern drawings. One is two pages on letter size paper, to be printed at 100% size (do not use "fit to page" when printing) and the other is for people with access to printers which can print Tabloid size (17" x 11") paper, to be printed at 100% size (do not use "fit to printer" when printing) so that the pattern can be all in one piece. If you feel I've made any errors in redrawing the pattern, please let me know and I will make revisions and upload again. Enjoy and feel free to redistribute.

Found a matching transformer, stripped some old telephone wire, scaled up the pattern and placed it on a 5 gal bucket. The taper on the bucket made it a bit of a challenge, but with some hacking and cutting the project is done and works. I live the boonies so only getting about 10 good channels. Gonna try again without cutting the bucket, and lay it out by hand. Then hang it in tree outside, also considering adding an amp.

stellar instructions with great results


I would like to know how did you come u with the pattern? What are the parameters you considered?

How would the frequency affect the design? Our desired frequency is 198-204 MHz.

Larger diameters of wire should work better at receiving signals, with the trade off being that they are more difficult to thread onto the form and to bend into the sharp corners of the fractal pattern. I have used 18 gauge wire with good results.

My printer refused to print the design beyond 100mm. no matter what settings I choose. what difference does this make to have it off by 50mm?

How did you measure antenna impedance? How do you know it is 300 ohms? How does it change with frequency?

I just tried my hand at making this (wanna watch Cosmos :D)

But unfortunately I cannot get it to work at all!

I used copper wire & followed the instructions. The only think I can think of is I used a Matching Transformer to connect the antenna to an aux cable/TV

In doing this I wrapped the copper cables to the pronged ends of the Transformer cables. Might this be the issue? Do I need to strip the ends of the transformer and remove those pronged ends?

1 reply

You don't need to remove the prongs; however, you do need to connect the antenna to the Antenna (ANT) input on your TV. The Aux/Cable inputs use different types of signals, such as those coming from DVD players, DVRs, etc., and will not work with an antenna connected to them.

I printed out the pattern for your Fractal Antenna about a year ago and just now made some time to build one. I found some thin plastic to weave the wire through and it does make a good all round general purpose antenna. Much better than the rabbit ears I had been using on our secondary TV. I assume because it is much more omnidirectional.

I was curious, since it took so long to thread the wire, if the antenna would work if I drew it using some conductive wire glue I had on hand (bought previously from Radio Shack). I drew one on cardboard this time and let it dry overnight. Sure enough, that works fairly well too. I used #4 screws and flat washers to make the connections between the carbon traces and the 300 ohm cable. Hot-melt glue works very well as the cable strain relief for the rigid antenna cable.

Some stations came in better while other not as good. That just tells you that these antenna are a little position sensitive, but of course they would be, give the size and operating frequency. One pointer, if using conductive ink, is to bend the cylinder into position before the ink sets up fully, since it is likely not very flexible and may crack when bent after it has dried. There are much better conductive ink pens out on the market and I would expect them to work much better than what I used but I was really surprised to see how well this worked too.

Was curious to know how you came up with the pattern? More specifically the inside pair of traces?

1 reply

Thanks for the good comments and the report on using conductive wire glue. I spent some time thinking about ways to mass produce the antenna, and it seemed that some form of printed circuit using conductive ink would be the best way to mass produce the antenna. I got busy with other things and never got around to experimenting with conductive inks, so I really appreciate your report.

After seeing a TV program about the fractal patterns used in cell phones to give them a very wide bandwidth, I went on line and did a search for 'fractal patterns' and found the Koch Snowflake as an example of a fractal pattern. I had only been aware of fractal patterns like the Mandelbot (SP?) patterns that were used to generate the incredible patterns is some screen savers years ago, and I couldn't imaging using something like that to make an antenna. So, I choose to experiment with the snowflake because it is so easily reproduced in wire. The inside traces were just an attempt to improve the antennas lower frequency response and were a lot easier to add than the effort that would have been required to punch all the holes and lacing wire that further duplication of the outside pattern would have required.

I made mine from some left over Cat 5 wire and an USPS Priority Mail box instead of poster board. If you cut the box right you don't even need tape as you can use the box's adhesive strips for that!