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How to make a fractal antenna for HDTV / DTV plus more on the cheap

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This instructable is from:

http://ruckman.net/archives.htm#FEATURED

and submitted by William Ruckman of http://ruckman.net

The first thing I would like to discuss is a little history, theory, and uses for fractal antennas.

Fractal antennas are a recent discovery. First discovered back in 1988 by Nathan Cohen and later published and patented in 1995. A fractal antenna has a few unique attributes as seen in this definition from Wikipedia:

"A fractal antenna is an antenna that uses a fractal, self-similar design to maximize the length, or increase the perimeter (on inside sections or the outer structure), of material that can receive or transmit electromagnetic signals within a given total surface area or volume."

What exactly does that mean? Well, you need to know what a fractal is. Also from Wikipedia:

"A fractal is generally a rough or fragmented geometric shape that can be split into parts, each of which is (at least approximately) a reduced-size copy of the whole,a property called self-similarity."

So basically, a fractal is a geometric shape that repeats and appears over and over no matter how far out or how far in you zoom magnification.

Source: Wikipedia and http://patimg2.uspto.gov/.piw?PageNum=6&docid=US007088965 Patent number: 7088965]

Fractal antennas have been found to be approximately 20% more efficient than normal antennas. Which could be useful. Especially if you want to make your own TV antenna to pick up over the air digital or high definition video, increase your cellular range, wifi range, FM or AM radio reception, and so on. Most cell phones already have built in fractal antennas. If you noticed in the past few years that cell phones no longer have antennas on the outside. That is because they have a internal fractal antenna etched on a circuit board which allows them to get better reception and pick up more frequencies such as bluetooth, cellular, and WIFI all from one antenna at the same time!

Wikipedia info:

"A fractal antenna's response differs markedly from traditional antenna designs, in that it is capable of operating with good-to-excellent performance at many different frequencies simultaneously. Normally standard antennas have to be "cut" for the frequency for which they are to be usedand thus the standard antennas only work well at that frequency. This makes the fractal antenna an excellent design for wideband and multiband applications."

The trick is to design your fractal antenna to resonate at what ever center frequency you wish to receive. Which means it will look different and be sized different depending on what you want to receive. A little math can be used to figure this out. (Or a online calculator)

In my example, I am going to make a simple one but you may want to make a more elaborate one. The more elaborate the better. I will use a spool of 18 Gauge solid core wire to make a antenna as an example but you could go as far as to etch your own circuit boards for aesthetic reasons, to make it smaller, or more elaborate with more resolution and resonance.

I am going to use the example of making a TV antenna for digital or high definition reception for over the air broadcasts. It is easier to work with these frequencies and they fall around half a foot to a few feet in length for half wavelengths of the signal. I am also going to base it off a common dipole antenna for simplicity and cheapness of parts for VHF. For UHF you may want to add a director or reflector which will also make it more direction dependent. VHF is direction dependent as well but instead of pointing directly at the TV station like UHF you want VHF rabbit ears (dipole antenna) to be perpendicular to the TV station. But there is a little more design to that. I want to keep this as simple as possible as it is already a very complex subject.

Basic supplies (cost me about $15):

Mounting surface such as the plastic project enclosure (8"x6"x3"). http://www.radioshack.com/product/index.jsp?productId=2062285
6 screws. I used steel self tapping sheet metal screws.
A impedance matching transformer 300 ohm to 75 ohm. http://www.radioshack.com/product/index.jsp?productId=2062049
Some 18 gauge solid hook up wire. http://www.radioshack.com/product/index.jsp?productId=2036274
RG-6 coaxial with terminators (and rubber jacket if mounting outside).
Aluminum if using a reflector. The enclosure above came with one.
A sharpie marker or equivalent preferably with a fine tip.
Two pairs of small needle nose pliers.
A ruler of at least 8 inches.
A protractor to measure angle.
A drill and drill bit that is smaller diameter than your screws.
Small wire cutter.
Screw driver or screw gun.

NOTE: The bottom of the antenna is to the right of this picture where the transformer sticks out.
 
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williamruckman (author) 1 year ago
I have made some new elements using a paper template I made in Gimp (photo editor). I used small solid core wire from telephone wire and it was solid enough, small enough, and malleable enough to bend into the intricate shape required at the selected center frequency (554Mhz - as this is the mean of the digital UHF over the air TV channels in my area) and iteration of the chosen fractal design. Which is repeated triangles.

Photo attached. It may be hard to see with the photo taken in low light, the color of the cardboard, and the color of the copper with tape over it to hold it in place. But you get the idea.

At that size the elements are pretty fragile, so they have to be handled carefully.

I have also attached the template in png format. For it to print the proper size, you have to open it in a photo editor like Gimp. The template isn't perfect as i made it by hand with a mouse, but it is close enough for human hands and a needle nose for bending of the elements.

Enjoy.
fractal.pngfractal.jpg
MrEggsalad made it!2 months ago

I took some copper wire and an old coat hanger to create my fractal antenna. It works really well, certainly far better than a standard ~$15 antenna and references suggest it works as well as the best of indoor antennas and even a decent amount of outdoor antennas. I did notice that initially my reception was lower than anticipated, but I upgraded the cable used to connect the antenna to my TV and that fixed those problems which were likely due to poorly shielded cables.

WP_20130930_022.jpg
Dalmo9 months ago
Hy guys! May I do the Fractals with 12AWG wire? Because this wire we have!
Txs
Peace
SpikeG7910 months ago
Just made 2 of these 'fractal stars' design that is in ToriAmos' post to add to my original Ruckman design antenna and gained about 5-10% signal strength on all channels. Very impressed :). I added them to the screws that held the transformer terminals. The 5 major network channels now come in @ 80-100% from 70-90%. One new local lower powered station strength went from 50% - 65-70% and is now watchable. I made them with 20 inch lengths of coat hanger wire so there's about 1/2 inch between bends, they take up about 5 inch x 5 inch square area. If I would have made them 10"x10" square area you would need about 40 inches of wire and 1 inch between bends. Hope this info helps.
SpeakerBoy1 year ago
I've made a version of this using ¼" adhesive-backed copper foil tape (the kind used by stained-glass hobbyists) applied to a sheet of acrylic, (without a reflector) and the results were both beautiful (think "Copper Snowflake Sun-Catcher") and impressive. By printing out your template and lining it up with match lines I put on the backside of the acrylic sheet, I was able to apply my strips of foil directly over it in the appropriate places. The adhesive is NOT conductive, but a few well-placed needle pricks soon cured that problem. Once I found the "sweet spot" in my bedroom window, it was performing just as well as my Gray-Hoverman (with reflectors!) while taking up a fraction of the space. It's an elegant little solution for apartment dwellers! I can't thank you enough!
Foil.JPG
jschwab3 years ago
I've modified the design to increase fractals, adding another set of fractal "whiskers" giving 3 sets per side and iterating the fractal shape several more times, while still fitting into the same compact space.

bending the wires is a little time consuming, but in theory it should add more stable reception. i thought it might be helpful if anyone else was curious about increasing the fractal bends.

Attached here is a pdf for use as a guide / template.

Also, this can easily be mounted to cardboard, pexiglass etc and placed INSIDE the project box, to conceal the antenna.
On the 2nd design fractal antenna. The distance between the bends is much less that the 1" on the 1st design. What should the distance between the bends be on the 2nd antenna?

Thanks,
Are there a couple of segments missing from the free end of each loop? It seems like there should be 5 small identical loops within each main loop. I have a modified version and would really appreciate it if someone could tell me if I have done it right.
for this design do you use all 6 fractals or could you use four like in this ible?
At what size should I print this template to achieve the same center channel as the one from the main instructable?
I printed mine at the default printer setting for a full 8.5 x 11 page. hope this helps.
So, does the image take up the whole page?
If you print with no scaling it should take up a little more than half the page. mine came out centered on the sheet of paper, with the longest edge measuring around 6 inches.
Thanks for the help, and thanks for an awesome Instrucable.
Using this design, how would I attach the dipoles and transformer
you would attache dippoles the same way as the original, at the apex or top of the fractal "star" pattern.
I used your increased fractal design. I got very good reception from an 8x10" surface area. I did not get notably better reception than this design: http://uhfhdtvantenna.blogspot.com/

but the fractal design is smaller and safer (no pokey bits sticking out).
Both designs are electrically the same. One design just happens to take up less space, which will let you cram more antenna into the same space--which makes them work better. More antenna == more gain == better reception
jschwab jschwab3 years ago
update: the original design gave me 56 channels.

with increased fractals (like the pdf above) i now get 88 scanned channels (southern california). that's a pretty significant improvement.
jkunken jschwab2 years ago
I have used DIY homemade antennas within the last two years to receive HDTV with no complaints. Decided to try out this new antenna model for kicks and giggles. With the increased fractal resolution, along with a reflector, we were able to pick up channel 38.1 beaming from Santa Barbara, CA directly from San Diego, CA, over 170 miles away. Signal strength and quality were both > 50%.

With the reflector and this type of antenna, directionality is key. By shifting the antenna's azimuth by only 12 degrees East, we lost Santa Barbara and began picking up Mount Wilson's signals (pretty much all Los Angeles channels), also from San Diego (only 100 or so miles away); still damn good, however, reception is tightly locked, though also *very* stable. Sans reflector, there is an increase in the number of channels from adjacent broadcast antennas, with additional stability introduced from the fractal design.

Great job.
Hi jkunken. Your input on the Fractal antenna caught my eye since I live in the San Diego area as well. If I may ask, on these channels your getting from Santa Barbara and LA area, is your antenna still the same size (perimeter) as the one shown being made here with just more fractrals? And is it mounted outside and elevated? You could be in a vary good spot for reception. Since I want to make one of these as well, I'm waiting with antisipation. Thank you. Garrison
Hi garrison111,
we used the increased fractal design as a basis (same perimeter). We then mounted the antenna on the focal point of a Dish Network satellite dish, with the dish facing North, from San Diego. The dish sits on our balcony; second story, though we also have trees in the way. It has been several months since the system was put in place and we still receive 50+ channels, mostly from Los Angeles, though we also receive adjacent channels from San Diego.
Thank you for replying jkunken. I'm sorry I didn't get back sooner. My Mother is recovering from surgery. Using the focal point of the Dish Network sat dish was brilliant! Because of the dish being a parabolic shape, it means everything being reflected is hitting the antenna. Great Idea! I have several questions if I may ask. Where would I look to get get a used sat dish? Is the antenna still mounted in a vertical (up-right) position or is it turned 90 degrees on it's side as shown in one of these photos that someone did? Are you able to get any lower band channels, say 2 ~~ 13?
I few years ago, I bought and put up the most powerfull antenna that Wineguard makes. I live a little way down from the top of a hill in National City. The antenna, 9 feet by 14 feet was raised 48 feet from the ground. I was able to get a lot of channels out of LA as well but they were unstable coming in out all the time. The wind from a storm in Dec of 09 blew my telescoping pole system in half. And that was the end of that. But you managed to do the same thing with far less. Are your LA channels and beyond stable? Thanks for your input jkunkin and waiting your reply. garrison 111
Garrison111,
yes, the satellite dish increased the gain quite a bit. The antenna is mounted vertically, not on its side, and in fact, most of the stable LA channels the antenna receives are in the VHF range (2 - 13), in addition to a variety of foreign language channels in the UHF range, of course. This is remarkable since DTV reception is based on the UHF range, afaik. One of the keys to stability is minimizing the use of splitters, since the signal can drop by several dB, as well as keeping coax cable lengths to a minimum; the longer the cable the greater the reduction in stability, say, if the cable is moved around. I believe tripods and satellite dishes can be purchased for around $100 from companies selling OTA receivers.
Good luck with your project.
I was wondering jkunken. You mentioned you used the increased fractal design. I assume you mean with the extra iterations. The first design showen here by Ruckman has two sets of wiskers. There's another called increased fractal pdf using three sets of wiskers. Is that the one you used? It looks as though measured in a stright line from one end of the wire to the other end would be 3 inches long with the iterations along the way. But the print outs show them being smaller. Were yours 3 inches also with the extra iterations added?
It's great that this antenna can pick up both UHF and VHF bands. On the loss of db, if an amplifier is placed close to the antenna, that should compinsate for line loss.
On the dish search, I jsut remembered. I believe and have seen them being sold on craigs list pretty cheap.
Thanks again and waiting your reply. ~~ garrison111
Not sure what is the true size of the fractals as my printer has scaling options. If I select no scaling of your .pdf file the the antenna footprint size appears to be about 6" X 8".

Thanks
gerry19461 year ago
OK I'll try this again.

I built the fractal antenna shown in the attached picture. Works great. I am 35 miles south of Milwaukee, WI and I receive 20 - 30 stations clearly. I can get Chicago stations but I must rotate the antenna.

Please comment on the circular design that I plan to build. Will it work if there are 20 fractals on the large diameter and only 11 on the small diameter. The large circle is 20 inches in diameter. The small circle is 18 inches in diameter. The fractals are approximately 3 inches tall.

Thanks for posting you instructions for the fractal antenna. Much better than my V shaped coat hanger design.

Sorry if I get multiple images. ??????
Antenna 002.JPGIMGP0566.JPGAntenna 002.JPGIMGP0566.JPG
Ok, it seams that you have used 1" distance from reflector. The other thing I wanted to ask is how you got to 1" of length of each fractal part? How this antenna performs on UHF and how on VHF?
Thanks
Could you please write what is the distance of the wire from the reflector?
whang071 year ago
I do not plan to acquire this.
whang071 year ago
Thanks to my wonderful application.
captsomer5 years ago
I understand what you are doing here but I think the diagram is a bit confusing. At the top of the picture, the first bend is labeled "60deg". Really its a 120 deg bend. I know its bent 60deg from straight, but I think the picture is confusing. The next bend is correct but the third bend is the same problem as the first. I just used 120 deg bend then 60 deg bend and then 120 bend and so on...
YUP! cool instructable but fix that diagram please
williamruckman (author)  captsomer5 years ago
You are correct. i imagine it as if there are straight lines there. I say 60 degrees because they are suppose to be equalateral triangles. And equalateral triangles have 3 60 degree angles in them.
jhitesman2 years ago
I've been thinking about making one of the usual coat hanger antennas for awhile...but the $12 commercial antenna I got off ebay a few years ago has been working so I kept putting it off. Well that one finally fell apart so yesterday I gave this a go. Works great! I have it sitting on a ledge about 7' off the ground aimed in roughly the right direction and get as good or better signal on all channels than I did with my commercial antenna at 20' and carefully aimed!

Took me less than 30 minutes to toss together. I just put some aluminum tape on the back of the chunk of scrap wood I built it on as a reflector - not optimal but seems to work just fine. Even if I count my wages for the time spent making it I'd say I'm time and money ahead vs. buying another commercial antenna - took me less time to build this one than it did to find a good deal on the last one I bought. And no waiting on shipping :)

The only downside is that 1 hour of TV last night reminded me why I don't bother with cable or sat anymore and seldom turn the TV on even when I have a working antenna :)
bdaniel72 years ago
Can't this be adjusted so that it receives all VHF and UHF frequencies in the same build?
jonny de2 years ago
also if i dont have dish or cable will i still recieve the signal?
jonny de2 years ago
how did you test your results?
and can i use 18 guage speaker wire?
feltonite4 years ago
 Pardon my ignorance, but what materials do you use for the reflector?
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