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

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 usedand 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)  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 de3 years ago
also if i dont have dish or cable will i still recieve the signal?
jonny de3 years ago
how did you test your results?
3 years ago
and can i use 18 guage speaker wire?
feltonite5 years ago
Pardon my ignorance, but what materials do you use for the reflector?
williamruckman (author)  feltonite4 years ago
It was an aluminum plate. Aluminum foil or aluminum/copper mesh can work as well.
3 years ago
I really want to design this antenna but I dont have copper, what of If I cut aluminium plate to the shape will it work? and Does size really matters? What it work indoor?? Africa
williamruckman (author)  howoigbe3 years ago
aluminum will work just fine. any conductive material will work. it will work indoors but not as well but that is the same with any antenna. size does matter, it can change the dynamics of the antenna. you can go to my website where i have links to a dipole calculator that will help you make the right size.
3 years ago
1.Note: I want to use Aluminum Sheet to cut the shape not cable type, will it still work??? 2. Give me dipole calculator url??
williamruckman (author)  howoigbe3 years ago
Yes, it will work. Here is the URL:

http://www.kwarc.org/ant-calc.html
3 years ago
link is broken- I am looking to make one for my Sansui TU-717 FM Tuner- thanks! (http://www.flickr.com/photos/48136705@N05/4607622985/)
3 years ago
1. Can Omni Antenna be used for TV?? 2. Do U have free energy tutorial. e.g magnet???
3 years ago
I need ur support on free energy like this http://www.youtube.com/watch?v=YNHOtzgTok8 . I want to construct one. Thanks
4 years ago
William,

Thanks for the instructable!  It is really cool.  I came across your design the other day and decided to try it out this past weekend and it worked pretty good, just in my living room and with no reflector.  My antenna is made with 8 dipoles instead of 4.  I sort of combined your design with the bowtie design.  I was able to pick up all the same channels as my two uhf only antennas from Radio Shack.  Granted I had to rotate the antenna to aim it in the right direction and not all signals came in as strong.

The antenna is not totally finished.  It's still missing a reflector.  I've read on some other sites that wire mesh might work better as a reflector, as opposed to a sheet of aluminum.  What do you think?  Also, is the distance between the dipoles and the reflector important?  My dipoles are on mounted on 1/2" plywood stick.  If I put the reflector on the opposite of the plywood, would it be too close?

I am going to try to add this antenna with my existing two in the attic and combine all the signals into one to see if it will improve my reception.  I plan to point all three in slightly different directions to be able to pick up all the stations.  I don't have a rotator.

Thanks again for the cool design.

Computothought3 years ago
Copper is at a premium so a made a foil version of your antenna. I am very impressed.
econtrerasd4 years ago
Would it work if you etched the design on a cooper board?, That way you could create a complex fractal easily.
3 years ago
WHAT IS A "cooper board"? Do you mean a Printed Circuit board? Yeah, that should werk.
.
There is probably a way to print it with conductive ink... then you could glue it onto about any (insulating) material you have handy, connect the terminals to a tranformer or a cable connector and plug it in! ,
If it gets damaged or worn print out a replacement!  Even print several copies and build an array.
.
Tin foil or a matel screen (strainer, etc.) makes an excellent reflector. Suggest you experiment with tin foil, scissors and scotch tape.
3 years ago
I'm sure "cooper" is a typo for "copper"
jimvandamme3 years ago
I just thought I'd show you a picture of one of Nathan Cohen's early fractal antennas, which I just happen to have. (He built it for my lab over ten years ago.) I can't tell you how big or wideband, but let's just say it is VERY wideband and compact. That all came at a price, as you can see from the S21 plot (transmission from one antenna to its twin): it seemed to have a lot of variations in the response due to the tortuous path the fields go through. I'd expect this one wouldn't be a good TV antenna, sucking out parts of channels. But that's the magic of fractals, you optimize until you get what you want.

BTW your average log periodic (fishbone-looking) antenna is also a fractal.
coersum3 years ago
I made an antenna following this instructable and was wondering if someone had an idea to help me out.

My problem is, I live about 45 miles from the towers (Beaver dam to towers in Madison wi), I get awesome reception with this except for 2 stations that I want.

I was wondering if there was a way to boost reception other than adding an amplifier and without making it bigger. As you can see from the pictures I added a couple elements to the original design to get a better reception.

Aluminum paper on reflector ? can I add straight elements going out of the ones in ?

Thanks for the help!
PS: yes I used a cookie cooling rack I had laying around :)
3 years ago
First, go to tvfool.com, type in your location, and get a map of where the TV stations are. They might be in a different direction. You can also see how strong they are.

Next, you're using the cookie rack horizontally polarized and the antenna elements vertical, so the signal isn't going to bounce off the back but go right through it. Also, the signals are horizontal, so turn your elements 90 degrees from the picture and you've got it right.

Doubling your antenna size will get you less than 3 dB so there's a diminishing returns. Better to try to get it higher, especially above any obstacles such as houses or trees.
3 years ago
PS:
I forgot to mention, I used the 1" setup, I have a piece of 2x4 (aka 1.5" between elements and reflector or however it's called :)
George35734 years ago
I am truly pleased with the design. Would you think that there would be much of a modification needed so as to be able to build one for a Wifi for computer Use?
Do you think that you might consider this Idea for the future?
Thank You. Nice project.
3 years ago
WiFi is narrow band (2.45 GHz), unlike TV. The fractal elements make an antenna wideband. You're better off making a narrowband, directional antenna to reject unwanted signals and get the gain you need towards the modem. Plenty of soup can antenna designs around.
plasticpopcorn43 years ago
Does the wire need to be unshielded or is it just easier if it is?
leemck3 years ago
This is the William Ruckerman 2009 Serpenski gasket fractal dipole based antenna for TV band reception.

Has any reader written a nec description file so this antenna can be modelled using the xnec2c antenna software program?

xnec2c is a Linux antenna modelling program. There are similar programs for Windows.

What a fine accomplishment in bringing the recent development of fractal antennas down to a practical and build-able level.
killersquirel113 years ago
Hey

Wouldn't the bending go a lot easier if you just pounded a nail into a board, then marked off a dot @ 1 inch on one side then 2 more @ 1 inch after the bend for 60 and 240 degrees?
jschwab3 years ago
This antenna works great. Also, you can mount this to a circuit board, or just some cardboard and place it inside of the project box for a cleaner concealed look.

This works as good or better than the \$50 clearstream micron i purchased from best buy.

I am also interested in more iterations on the fractal design, but i cant imagine id be able to tell the difference as i already get 50+ channels with this. if only 40 of them werent in foreign languages. :)
greengraff3 years ago
good day sir . . . . . . can i use mesh screen for reflector ü
charlie.nourse3 years ago
Would a coat hanger work for the antenna?
avengine3 years ago
this is a very cool project, just curious to know before you do this did you also compare the design of this to db4 & gray-hoverman antenna design. I think your design has the smallest area, and more simple to build. On the other hand I want to know is there anyone has any chance to compare the strength of this 3 design and find out which one get the best result.
thanks again for the great instruction.
My mom wanted to dump cable, but could not get a dish because of her condo association. Doing a little research on TV antennas, she opted to buy a Philips indoor/outdoor antenna, with full low/high vhf & uhf receiving capacity (channel 2 thru 69), with a 40 mile range. Her neighbor bought a Terk indoor antenna with similar specs, but with a 45 mile range. They live about 35 miles southwest of the Chicago TV broadcast towers.

The Philips received only 2 channels, very badly. The Terk received none. So I decided to build her an antenna. After weeks of research, I decided to combine a few designs. I found the basic fractal design on Ruckman's sight, but changed it slightly. See attached drawing/photos.

I came up with a picture frame antenna that works really well. I live 25 miles northwest from the broadcast towers. The day I tested this antenna it was raining and jets were flying directly over head of the house ( 200 to 300 feet above). It should be noted that the jets disrupt the roof antennas signal.

Every station came in clear, no problems, even channel 2 (cbs) which is the hardest station to get (low vhf band). So I took it into the basement. Totally below grade, steel, concrete, not signal ever was received before. This antenna received all stations clearly, even channel 2. I couldn't believe it.

Took it to moms. Placed it on her TV (54 inches off the floor. Got every channel but channel 2, very cleanly. She's using it as I write this. Channel 7 (abc) which is also hard to get (also vhf), comes in better than it did on her cable.

I'm working on a better vhf antenna to try and get her channel 2. Hope the pictures make it.

TOTAL ANTENNA 1.PDF(1512x575) 2 MB
3 years ago
It is incredible how this simple design grew legs and run like this. I watched NOVA: Fractal on PBS once and was searching about and found this instructable. INCREDIBLE! To the first INVENTOR "thank you, Sir!" And, this refined model I thought to claimed this first once realized to expend the design by the fractal pattern from wikkipedia but you posted first so you are the MAN! Regardless, "WHO" was on first since this first simple design was free and the subsequent designs are also F.R.E.E and I am here to say "why would anyone pay more...for an antenna?" I reside in San Diego area but reaching to get LA stations with expensive antenna...yup DB8 but no luck so now for cosmetic reason to the house I reverted to this design and settle for just the local stations it is absolutely fabulous!

Gentlemen, you are geniusesseess!
4 years ago
I've made your version of the antenna with 1/2" bends (for a total of 9" per branch or 18" per element with 12 gauge wire). the only variation is that I've also kept the 9" distance between the elements and connected the balun at the middle (4.5").

from my tests (15 or so miles away from the towers, all in the same direction) I'm indeed getting very good results and constant signal for UHF, as expected (all channels 80-100%, mostly between 90-100%)

on the other hand one channel using VHF 7 is only 40% and quite constant, but when cars pass by the street i get breakups. i assume i could improve signal by adding a reflector and moving the antenna to find the "sweet spot" where all channels are in best shape.

overall I'm not sure there is much difference between this one and the normal "V" shaped element DB4 antenna, other than smaller size. it may work better if drawn on a PCB.
4 years ago
OK i tried adding a reflector in various positions up to 6" from the elements and it made the signal degrade significantly up to being lost on most channels. not sure if it's just my particular case or if the reflector for this kind of antenna shape makes the signal worse generally.

moving the antenna (without a reflector) around a bit increased channel VHF 7 to about 50-60% and slightly degraded the others to around 80%. I'll do some more experimenting, maybe adding an amplifier into the mix over the next few days.
4 years ago
i've tried your original 1" distance between the stacked elements (about 6" on center), but it's getting worse signal, especially on VHF 7 so i'm back to my 9" distance on center between them. the reflector at any distance made it definitely worse.

overall my bi-quad antenna with reflector (looks like a squared number "8" with a 5" arm length) beats this one in both UHF and VHF (channel 7).
4 years ago
Hello,

Could you tell me how you connected the 4 dipoles to the two center wires and the tabs for the matching transformer?  Did you solder them?  And did you bend the copper wires by hand?  That must have been tedious.  I would like to try your design and was trying to figure out how to go about doing it.  Thanks.
runninutes4 years ago
I've been thinking about making one of these, but was thinking about iterating once more on the fractal. However, there's an important question that I hoped someone could help with. Which is the important length? The overall length of the wire, or the length of each segment?

That is, the pattern calls for 8 inch wires bent into 8 segments of 1 inch each. Is the 8 inch length the important part for the calculation of what frequencies I'm trying to catch, or is it the 1 inch measurement? Thanks!
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