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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

Showcased in the March 2015 issue of Popular Science Magazine:

http://www.popsci.com/learn-defy-cable-company-diy-hdtv-antenna

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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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
spiralciric3 years ago
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
spiralciric3 years ago
Could you please write what is the distance of the wire from the reflector?
whang073 years ago
I do not plan to acquire this.
whang073 years ago
Thanks to my wonderful application.
captsomer6 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)  captsomer6 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.
jhitesman3 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 :)
bdaniel73 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?
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)  feltonite5 years ago
It was an aluminum plate. Aluminum foil or aluminum/copper mesh can work as well.
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.
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
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/)
1. Can Omni Antenna be used for TV?? 2. Do U have free energy tutorial. e.g magnet???
I need ur support on free energy like this http://www.youtube.com/watch?v=YNHOtzgTok8 . I want to construct one. Thanks
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.

Copper is at a premium so a made a foil version of your antenna. I am very impressed.
econtrerasd5 years ago
Would it work if you etched the design on a cooper board?, That way you could create a complex fractal easily.
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.
I'm sure "cooper" is a typo for "copper"
jimvandamme4 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.
fractal-antennasmall.jpgfractals-10ft apart.gif
coersum4 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 :)
SANY1745.JPGSANY1746.JPG
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.
coersum coersum4 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.
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.
Does the wire need to be unshielded or is it just easier if it is?
leemck4 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.
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?
jschwab4 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. :)
greengraff4 years ago
good day sir . . . . . . can i use mesh screen for reflector ü
index23.jpeg
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