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 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.

Step 1: Adding the reflector

Assemble the enclosure with the reflector under the plastic cover.

Comments

[williamruckman]

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.

[SpeakerBoy]

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!

[jschwab]

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.

[moffett8]

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,

[ToriAmos]

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.

[Lee_Smith]

for this design do you use all 6 fractals or could you use four like in this ible?

[festizio]

At what size should I print this template to achieve the same center channel as the one from the main instructable?

[jschwab]

I printed mine at the default printer setting for a full 8.5 x 11 page. hope this helps.

[festizio]

So, does the image take up the whole page?

[jschwab]

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.

[festizio]

Thanks for the help, and thanks for an awesome Instrucable.

[blong1024]

Using this design, how would I attach the dipoles and transformer

[jschwab]

you would attache dippoles the same way as the original, at the apex or top of the fractal "star" pattern.

[jsilverman1]

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).

[Spokehedz]

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

[dmoore19]

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

[jschwab]

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]

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.

[garrison111]

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

[jkunken]

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.

[garrison111]

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

[jkunken]

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.

[garrison111]

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

[gerry1946]

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. ??????

[spiralciric]

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

[spiralciric]

Could you please write what is the distance of the wire from the reflector?

[whang07]

I do not plan to acquire this.

[whang07]

Thanks to my wonderful application.

[captsomer]

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...

[da winksta]

YUP! cool instructable but fix that diagram please

[williamruckman]

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.

[jhitesman]

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 :)

[bdaniel7]

Can't this be adjusted so that it receives all VHF and UHF frequencies in the same build?

[jonny de]

also if i dont have dish or cable will i still recieve the signal?

[jonny de]

how did you test your results?

[jonny de]

and can i use 18 guage speaker wire?

[feltonite]

 Pardon my ignorance, but what materials do you use for the reflector?

[williamruckman]

It was an aluminum plate. Aluminum foil or aluminum/copper mesh can work as well.

[howoigbe]

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]

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.

[howoigbe]

I need ur support on free energy like this http://www.youtube.com/watch?v=YNHOtzgTok8 . I want to construct one. Thanks

[howoigbe]

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]

Yes, it will work. Here is the URL:

http://www.kwarc.org/ant-calc.html

[Om_Audio]

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/)

[howoigbe]

1. Can Omni Antenna be used for TV?? 2. Do U have free energy tutorial. e.g magnet???

[curiousgeorge03]

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.

[Computothought]

Copper is at a premium so a made a foil version of your antenna. I am very impressed.

[econtrerasd]

Would it work if you etched the design on a cooper board?, That way you could create a complex fractal easily.

[RustBelt]

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.

[jsilverman1]

I'm sure "cooper" is a typo for "copper"

[jimvandamme]

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.

[coersum]

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 :)

[jimvandamme]

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]

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 :)

[George3573]

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.

[jimvandamme]

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.

[plasticpopcorn4]

Does the wire need to be unshielded or is it just easier if it is?

[leemck]

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.

[killersquirel11]

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?

[jschwab]

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. :)

[greengraff]

good day sir . . . . . . can i use mesh screen for reflector ü

[charlie.nourse]

Would a coat hanger work for the antenna?

[avengine]

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.

[baddahbing]

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.

Baddahbing

[hankuruski]

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!

[DIYSlacker]

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.

[DIYSlacker]

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.

[DIYSlacker]

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).

[curiousgeorge03]

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.

[runninutes]

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!

[jmengel]

Built this last night, and it gives better SNR by 1-4dB on all channels in my area. My previous antenna was an amplified Philips. It only drew 3-5W but not having that plugged in 24/7/365 will save ~40kWh per year. Thanks for this great Instructable.

[lynchcon]

Great antenna! I upgraded mine to commercial materials and a little sheetmetal. how can i put a picture up. its over kill but i think you might enjoy. And it is the same size as the design just made two instead. i point one over lake ontario and one faces toward the cn tower. 19 HD channels. dont mock anyone. if you cant get channels try looking up tv towers in your area .

[servant74]

What would be the lengths for WiFi? Instead of 1" segments that is. I am guessing 32mm(1.26") long segments and a box 18mm(0.71") deep, rather than 25.4mm(1") and 76.2mm (3") deep box.

.

And how sensitive are the dimensions? ... Thanks.

[servant74]

What would be the lengths for WiFi? Instead of 1" segments that is. I am guessing 32mm(1.26") long segments and a box 18mm(0.71") deep, rather than 25.4mm(1") and 76.2mm (3") deep box.

And how sensitive are the dimensions? ... Thanks.

[erik61820]

i cobbled together a couple of these antennas tonite, I was able to get a chan they couldnt before with amplified rabbit ears, and I needed one. I can also get the same chan that I couldnt before with regular rabbit ears that had 5 foot whips.

They both work really well, One has a balun one doesnt..They both are superior to
the amplified & unamplified rabbit ears. The next time I make another I will probably solder things together and better the construction.

Thanks for the plans

[Houdinipeter]

Just had an idea. Could I solder the wires together instead of using screws? I'm using a piece of cardboard instead of the project box though.

[vulkr]

Thank you for the fantastic instructable. I was wondering if you could help me with the ideal center frequency pattern & size required for AM/FM HD RADIO for my car. The existing antenna blows and I have dropouts all over. My plan is to use thin aluminum foil strips in the required pattern and affix them to my rear window with custom-cut black vinyl sticker that really hugs the foil, minimizing view obstruction. The foil would be between the vinyl and the glass along the vertical sides of the window (and possibly the horizontal also) to maximize reception. The top of the foil patterns would terminate in wires that go to my car's OEM ceiling antenna rig (it's a 01 Jetta) through the headliner, and I'll cover the outer hole with a plug. I just need the ideal "center frequency" pattern & size for max resonance and best reception. Also, would I need a transformer? This version doesn't seem to have one: h**p://www.youtube.com/watch?v=tIwdNccmo_s ... Thanks in advance.

[vulkr]

PS I was wondering if FOIL TRANSFER using a laserprinter would work... That way the pattern could be incredibly intricate, more than possible with me cutting foil strips. Printing silver foil on black paper would be ideal. Example: h**p://www.texascraft.com/hps/product.php?productid=16972&cat=275&page=1

[melmocca]

are you sure that the reception you received could be as well be received by the dipole by itself?

[Cameron657]

The fractals are the dipoles. The line in between is called the phasing harness. It picks up extremely little.

[williamruckman]

It is possible, depending on the actual impedance of the dipoles which can vary. I had no way of measuring or easily calculating that so the easiest thing was to use a Balun. Depending on your center frequency it may work. Try it both ways.

[ka irnie]

sir good day,
                      if i will use a balun for this fractal antenna ,what impedance should i use?ntx.

[Cameron657]

A 300ohm to 75ohm Matching Transformer/Balun. Hope this helps.

[ka irnie]

Good day sir, I already made my prototype of this fractal antenna, I follow your suggestion to put a Balun 300/75 ohm matching transformer.Unfortunately I cant test it here due to that our broadcasting here is still analog,Have you tried this in your country? BTW I live here in the Philippines. Tnx. Best regards.

[nelu57]

750 ohm ? or 75 ?... Attention that you did wrong here !!! You know what you say?

[Cameron657]

Don't you know the difference between a o and an 0???????? I clearly said 75ohm! Also consider learning English before correcting me. "You know what you say?".

[nelu57]

Sorry if I wrote was wrong, but it can not read well. Makes you a space between words. Sorry of English spoken. I use a programme of automatic translation. Only good news.

[Cameron657]

Um, if you can't even speak a little English without a convert tool, then don't try instructing me on proper grammar.

[nelu57]

Professor you never wrong ? ... You get a perfectly man? at the age which is shown ? To no longer asked in vain Ok.? End !

[Cameron657]

You, sir, are very insulting, and I suggest you stop spamming my posts.

[Cameron657]

One word. Fantastic! I will have to make a 4 bay version of this. You have researched this well, your instructable is very simple and helpful, and the final product is very high powered. This gets 5 stars from me! I award this the Weegee097 Seal of Approval. Not many things get that, but this is such a simple and powerful antenna that it amazes me! Keep up the great work!.

[cchandler48]

I live in Niagara Falls, Ontario. I put two of your fractal antennas (built on 2x3 lumber) in my attic without reflectors pointed NNW (toward Toronto, about 60km) and SSE (toward Buffalo, about 40km). Each antenna has a dedicated 24db RF amplifier before they join into a RG6 downlead. No baluns as I found the signal loss from the balun was greater than that from the mismatch. Excellent reception on the US stations (all digital) and on most of the Canadian stations (they don't convert till August 2011) including TVO (analog ch 19). CBC is excellent (ch 5.1) as they installed a good digital transmitter some time ago and transmit from the CN tower. By all rights, attic antenna should not work here. Local dealer wanted to sell me a roof mounted DB8 for $250 plus installation. Nice work.

[ohh1941]

I made one for my sailboat and it outpeforms the special marine antenna and the rca antenna .it doubled the channels i get

[rvnutman]

thanks for the incredible idea.  My question is this.....looking to use this design with my pop up camper.  Would it be possible to rig up some type of PVC pole or mast to get it up in the air say 15-30 feet?  Just throwing some things around and wanting to make sure that it CAN BE done.  Generally take satellite with us, but I believe this would work well and looking forward to your input as well as the project.  The place where we go on our spring fishing trip is rural in nature, but I know some type of signal is available because I used some rabbit ears last year to make sure that I could receive a signal so I could watch my daughter on the news broadcasts.  Not a really good signal, but a signal.  With this set up, I hope that I can pull those local stations in with clarity.  Thanks for the advice and/or suggestions.

[Pukinpr]

Great Project! So far I've made two of these, one by your exact designs and one I modified to fit inside of the project box for outdoor use, by shortening the array to 3/4" segments but still maintaining the 60 deg. I also add an additional array and soldered it 1" above the first array. I had better success from the additional array, and it can pick up 12 DTV channels with great clarity. 

[curiousgeorge03]

I cannot see clearly where you soldered the second array to the first.  Can you post a close up picture of where the solder connections are?  Thanks.

I want to try the same thing and see if it improves my reception.

[laborracha]

 not criticizing the design, just the use of the word fractal.

[laborracha]

http://www.sciencprog.com/wp-content/uploads/2007i/fractal/koch_figure.png

[laborracha]

Not to nitpick, but I'm not sure those are technically fractals without one more level of self similar repeating scale. Without that next level you may not get the benefit of fractal antennas, which is the ability to pick up different frequencies. 

[williamruckman]

Yes, it would be best to go one more iteration. This is the first and initial build. I found that it worked great, so I shared it for everyone else to experiment with as well. But anymore iterations than one more, then you don't see too much more gain.

[jsmithblue]

 I am new to this, but what would more iteration look like? Is there a pic anywhere online i could reference?

[ElectricUmbrella]

Very nice! Do you think this could work for crystal radios as well?

[aeroengineer4]

 Question: can this type antenna be used to send signal and not just receive it? If so do you have any links or information you could pass along?

[Wyle_E]

In general, any passive (no built-in amplifiers) antenna can transmit as well as it receives.  In fact, in antennas with parasitic elements, like the traditional long-boom VHF TV antenna, it is customary to refer to the element that is connected to the transmission line as the "driven element", even in an antenna used exclusively for receiving.

[aeroengineer4]

 So on one like this how would you find the frequency if you are only wanting to use it for a limited range in frequency

[aeroengineer4]

 sorry I mean transmit on a certain range of frequency

[Computothought]

There are a thousand ways to make a dtv antenna. I would like to do a newer foil version like yours and see if there is any improvement.. 

[Buskieboy]

I'm dying to try this out this weekend.  I'm a bit confused as to where the reflector goes and how it's attached.  Is the plastic cover screwed to the reflector?  Or is it that we just make sure the project box has the antenna on the top and the reflector underneath?

[williamruckman]

The reflector was placed on the inside of the lid, opposite side of where the dipoles were placed. You just have to make sure the dipoles are isolated from the reflector.

[bertram00]

I notice all five of your channels are in the UHF. Have you been able to test the VHF? I need both in my area.

[williamruckman]

Yes, in my area, they moved most channels into UHF. But it does work on VHF as well. The dipoles can be adjusted to fit whatever center frequency you wish.

[Jon B3]

Could you use a blank CD or DVD? By that I mean the foil layer under the printed surface. It'd be a pain to "etch" out the design though.

[Jon B3]

Or how about using conductive thread and an embroidery machine?

[williamruckman]

That should work fine. If you get good results, let us know!

[hexopod]

 Can you recommend an easy way to adapt this for an N, or preferably SMA-type connector? I'd love to try one of these out hooked up to my 802.11g adapter.

[williamruckman]

You may need to buy ends and crimp yourself a custom cable. Although I believe the SMA connector for WIFI is 50 ohm. So, unless you buy a different Balun you may need to alter the impedance.

Something like this may help:

http://www.edaboard.com/ftopic201626.html

You will also need to change the size of the enclosure / dipoles to match what frequency range you will be using. It will be much smaller at native N (5 Ghz). Also, if you are using hybrid B/G/N then if would be best to buy a router with two transceivers and make 2 antennas. One for 2.4Ghz and one for 5Ghz and place each antenna on the separate tuner/transceiver.

[guitarra]

Hi all:
I built one  antenna like the one here using cooper wire and attached to the inside of my window. It went from 3  poor quality channels to  5 channels with a a great signal!

Thanks!
RL

[goodjobjohn]

Great project!!! I built this a few months ago while living in the mountains of western NC. I went from 2 channels to 8 with much clearer results. Recently moved to Boston and etched a version on copper clad board with the second fractal iteration. I went from 10 channels, which had almost constant breaks in the signal, to 14 with close to absolute clarity.

[acnjay]

Your etching looks top notch: What are the measurements of your antenna? And what tools did you use?

[ellisgl]

An array of 4 or 16 of those boards would be sweet.

[PnP1]

Very nice, Would you mind sharing what formula, if any, you used to layout the fractal part of the pattern? I'd like to make one but with one more fractal if possible. Peter

[williamruckman]

See here:

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

[Foxtrot70]

I like your antenna design. I just tried fractal design on a drawing of a Bowtie Antenna I made for my computer Data Card. On paper it reduces the area by about 60%, that is why they are used in cell phones, according to the PBS program "Hunting the Hidden Dimension" fractalization of the antenna improves antenna performance by as much as 20%, consider this for every 1db of improvement it doubles the signal strength. With that in mind that is why you went from 2 channels to 8 channels in reception. Lookin' Good.

[Johenix]

Last time I looked it took 3db to double a signal, 6db to quadruple a signal and 9db is 8 times stronger than the origional signal. 10db is 10x, 20db is 100x, 30db is 1000x etc. So 13db would be 20x, 16db= 40x.

You assumed that if 10db= 10x , 1db might equal 2x. An easy beginners mistake.

[Foxtrot70]

Your right this is a first time for me with antenna design.  The 1db =2x was from the program as I recall.  I stand corrected.  One can not help but to appreciate the elegance of the design.

[williamruckman]

It is actually 3.5dB

[williamruckman]

NICE!

[Vorg]

How did you come up with the new spacing between the elements? Or did you change it? To keep the element length at 8" you go from a triangle that is 3" on a side to one that is 2.25" on a side. I also noticed your connection points are not at the tip of the V. Any reason?

[williamruckman]

I modeled it after the DB2 HDTV Antenna with a fractal design. All my work and calculations are on my website:

http://ruckman.net

[Vorg]

I've tried to go through all the links, and I understand how to figure the starting length of the wire and making the fractal elements. It's the Vertical spacing between them. The Original non-fractal designs have around 5-6" spacing. The basic fractal design has 4" spacing. With another iteration the overall size is reduced more, but what about the vertical spacing between them? How do you get that number?

[Just-Mike]

Thanks for the great and easy to follow instructable! I built my antenna yesterday and now have it painted gray similar to a sat. dish. My HOA didn't really like my coathanger and wood antenna. I don't see them having a problem with this one. Now, I just need to tweak it a bit so I can pick up more channels. I'm missing a few Networks that I was able to pick up with the coathanger model.

[justinbmiller]

 Just wanted to say thanks. Thanks a ton, actually. It's been so long since I've built something since the move that I wasn't in the mood to really go too far into reading optional measurements for my area, etc. etc. so I just followed your guidelines and it worked like a charm. Crystal clear broadcast and PBS (plus about 50 other channels I'd never watch).

Also, I didn't follow to exact spec's: I used bailing wire for the fractals, a project container that was one size smaller (7"), and stripped Romex for the dipole antennae. Regardless, it still worked just fine. Thanks again, you have saved me so much money. I owe you a beer.

[fooble]

Hello.  I've read with great appreciation all the comments about fractal antennas.  It is astounding to me that Mandelbrot in the sixties saw patterns where you wouldn't expect them ... and, thus, order out of chaos.  This Father of Fractals allowed us, in a sense, to predict the unpredictable.  He also allowed us to now construct this new type of fractal antenna.  Kudos to all those, like William Ruckman, who have achieved success with this most simple and effective antenna.  I tried to make one, too, and even got the same (overpriced) impedance matching transformer from Radio Shack.  But, I don't understand it ... all I get is a blue screen.  I would love to see even the cursed NO SIGNAL banner, but all I get is that damned blue screen.  Can anyone help?

[williamruckman]

Not sure what could be the issue causing your blue screen. It might help if the community had more information as to the EXACT set up you are using. How you built the antenna, your type of TV (make/model), how it is all connected, what TV settings you are using, and some photos to go along with it.

[steve_newguy]

Kids wanted TV for Christmas, so I printed out the fractal picture (PDF file)  and taped it down on a piece of cardboard, drilled the holes and tightened the screws down on the four fractal shapes made of 16 gauge wire.

I didn't do the reflector bit.

I parked a digital converter box and the antenna on top of a bookshelf in my living room and get 14 channels -- including 4 educational  channels PBS all different. 

I was worried that reception would be lousy since I'm below a hill that blocks the line of sight with the majority of transmitters in this city.  There's also a lot of natural stone on the exterior and stone fireplaces that mess up WiFi signals.

I don't have to worry about the weather, so it might just stay on the cardboard.

[TZin]

Wire Bending Tool For Fractal/Conventional Antenna-making Plus Some General Performance Questions:

1) For what appears to be a well matched wire bending tool--iteratively speaking--see the following:

TED Conference video
TITLE: Arthur Ganson: Sculpture that's truly moving
http://www.youtube.com/watch?v=bPfn01Ndc1g&feature=channel
(mm:ss) 10:26 - 10:49

A drill press, a sharp bit, a hack saw, and vice appears to be all that is needed to make this two part hand tool.

Arthur Ganson is a machine and wire artist (and engineer). He makes kinetic sculptures.

2) Has anyone compared the fractal antenna to a Gray-Hoverman design,say, like this one?

http://blog.makezine.com/archive/2009/01/maker_workshop_dtv_antenna_steadyca.html

3) Wire: regardless of design, is heavy gauge better than light, as a general rule. e.g., Is coat hanger better than speaker wire in a significant way?

This uhf antenna business has been kinda fun these last few months. Made a GH for me and one for a retired neighbor using speaker wire, glue gun, and foamboard. Now, the fractal thing has my curiosity up again.

Regards

[TZin]

Minor Correction: My reference to the "GH antenna" (Gray-Hoverman ) for a friend and myself was based on the name given by a few websites to what is, in fact, a Whisker (or Bow-Tie) antenna.  My GH antenna came later, here:

Making a Four Iteration Koch Fractal Antenna for HDTV/DTV with Copper or Aluminum Foils, Part 1 of 2
www.instructables.com/id/Making-a-Four-Iteration-Koch-Fractal-Antenna-for-H/

Making a Four Iteration Koch Fractal Antenna for HDTV/DTV with Copper or Aluminum Foils, Part 2 of 2
www.instructables.com/id/Making-a-Four-Iteration-Koch-Fractal-Antenna-for-H-1/

[TZin]

Wire Bending Tool For Fractal/Conventional Antenna-making Revisited:

This video is the full version from my prior link. The TED link in the first comment actually shows the artist in a lecture with portions of this video on the screen behind him.

This video has great detail.
http://www.youtube.com/watch?v=f0UNz-ayzrE

Regards

[kipgynn]

I just finished building the a fractal uhf tv antenna based on the design above but also using the charts in TV Fool to customize the length of the antenna parts to my area.  I looked at the frequency of the channels in my area and found a middle ground between the highest and lowest and cut the segments according to the plug in charts provided. My antenna now has segments that are about 10 inches long instead of 8 inches
Previously, I was using a rabbit ear/uhf combo table top antenna that was about 40 years old and  and had lots of drop outs.  When I hooked up the fractal antenna using an Archer transformer similar to the one pictured, I got mixed to poor results.  I moved the antenna around and up and down within a 15 foot area and I got fairly poor results.

Today, I decided to try a different matching transformer with the same fractal antenna and the difference was HUGE! 
I used a "professional" or commercial transformer from the cable tv company instead. Now one of the stations is coming in at a strength reading of 52!
All I did was change the transformer and put the antenna in approximately the same position.
I highly recommend the tansformers made by a company called RMS and you probably can order them online or better yet, get an old one from your local cable company truck perhaps for free! It doesnt have to be RMS, just one that cable tv companies usually provide to their customers to hook up an old style tv to 75 ohm round cable.

I havent tried it with just a piece of flat cable....has anyone out there used that approach with no transformer at all? what were the results?

[Buskieboy]

Is this the plastic cover?  I am assuming the reflector is right up against the plastic cover?  Wouldn't the screws make contact with the reflector underneath?
Sorry for being such a noob, but I want to really make this and need some clarification on this part of the assembly.

[williamruckman]

This is the top of the box. The reflector and lid screw on the bottom and they are far enough apart that the reflector isn't contacted by the screws. In this case, the reflector fits into the bottom lid. It is internal.

[Buskieboy]

Ah, so you use the whole box as well!  It seems perfect for this project.
I see now, thank-you. 

[148wmcquiston]

Does anyone know how to make a helical fractal antenna?

[onwardft]

I built my first antenna on a piece of white plastic (I did not have a project box) and was very impressed at how many channels were received and also how well the signal "locked in" to the frequency and held without pixellating. Great design that I am using right now! Thank you I do have a couple of questions: (1): On a second unit I built, I had used clear plexiglass and did not get as many channels as the first one no matter how hard I tried and aimed. After re-reviewing the construction techniques, fractals, etc. and not seeing any obvious errors, I am now wondering if the difference between a solid color plastic background and a clear plexiglass background makes a difference in reference to reception and possible reflection and am wondering if I should take the antenna apart and paint the clear plexiglass? If this is the case, is there a difference in reception / possible signal reflection between a black or white background? The youtube video of this antenna (where I came to this page from) uses a white background but the pictures here show a black background. (2): I would presume that by adding more "fractal" pieces that antenna gain would increase. If I decided to make another antenna with more fractal pieces, should I place the fractal pieces above (4 fractals) and below (another 4 fractals) the current setup to increase the overall height of the antenna... or should I at least double the width and create another four fractal set (like the video) to the side and run wires in parallel to the other four fractal set. Also how far apart should the fractals be apart on the horizontal plane. Thanks for a great antenna and your help and support in advance.

[rt82]

In my area there are only 4 dtv channels that can be picked up, two are 480i and the other two are 1080i. I was curious to see if I can pick any up I made my first antenna. It was super simple. Just two coat-hanger wires positioned horizontally, stuck on a box with a aluminum reflector on the back. To my surprise I could pick up one channel 480i but it was choppy. Knowing that it was possible to pickup hdtv channels I came across this guide to build a fractal antenna. The antenna did help a little bit, that one 480i channel worked great and I could just bearly pickup another that was 1080i. Then I went ahead a built a much larger uhf antenna out of coat-hangers, I think they call it the bowtie. This let me get one of the 1080i channels and both 480i. I then decided to combine the two antennas and since the fractal antenna is so small I use it to tweak the signal for best performance. On my Sony tv it's hard to adjust as there is no signal strength meter but some fiddling makes perfect. Now I have the 3/4 channels working great, though the other 1080i channel eludes me. I did get it perfect once, but it seems it either works or it doesn't. I haven't realized just how picky these antennas are, they are super directional. A simple 1 degree adjustment and I'm already loosing channels. Do you guys think if I get one of those uhf amplifiers off ebay that will help?

[carrierpilot1357]

never mind the horrible drawing, but I have a question (said in the image)

[williamruckman]

I would say that you would want to use neither of these. Look up DB-2 (which is a similar design to my fractal antenna) and then look up the DB-4 and see how the two outer dipoles have the connections crossed and the balun is in the center of the antenna. The DB-4 may be what you are looking for but you will need another dipole.

[nghosh]

Instead of plastic, I have made this with a wooden board and haven't tried any reflector. Can someone please tell me why it is not working as expected, I am getting better signal with a paper-clip antenna than with this.

[bizzarro]

I just finished and installed one on the roof using the "8 piece" design. I connected the fractal antenna 14 feet below the old existing "yagi-uda" (I have a 20 foot g.i. mast) and joined them together using a splitter as a combiner. With a tv signal booster (amplifier), 2 local channels from the uhf band and 1 from the vl band became blurred but the remaing 13 channels improved. I found out that one local station was northwest and the rest are either north or 10 deg. northeast. Do I need to make a 3 dimensional fractal antenna (triangular or box in shape) to cover all the signals and will it work? or do I need to use LittleRose-68's pattern? PS. I live in the Philippines, no cable, no dtv or hdtv. Only 3 analouges. Thank you. and more power.

[technodude92]

I'd had this project bookmarked for ages now and finally, after a late cable payment resulted in a temporary TV outage, I got around to building it. Just some info on my particular build. In lieu of solid core wire, as I didn't have any at the time, I used an old metal coat hanger, sanded down to the bare metal. Also I didn't have a fancy enclosure, so I went with an old 2x4 which is the right width but a little long for this project. I'll cut it down to size in the near future. And finally I used some aluminum foil with a cardboard backing as a reflector. I love how compact it is and the quality I'm getting from an antenna that was basically thrown together in a few minutes. I have no means of objectively judging the quality but I can tell you it is much less finicky than my old dipole antenna and will definitely be replacing it.

[awdark]

Its not too bad but surprisingly not quite as stable as my UHF/VHF antenna (bunny ears with loop combo) my bends might not be precise enough so can't pass judgment too quickly. But its definitely not bad for something compact and pretty much free!

[fcampbell]

I'm surprised that this is the only instructable on fractal antennas. I've been reading these comments for a while and drawing fractal shapes to think about and was stuck on how to create them. Then I thought about conductive paint. A pen for drawing conductive lines is here: http://www.semicro.org/index.asp?PageAction=VIEWPROD&ProdID=142
Any opinions as to whether an antenna can be made by using conductive paint?

[tjuxed]

What about transferring the desired fractal pattern to copper clad board (aka PCB)? This would be an easy method for precise, complex patterns.

[williamruckman]

Anything that is conductive and bare can be used to make an antenna. Including conductive paint ;)

[HoldOnTight]

Okay, spent today figuring out the details of the new design. I tested it, but it isn't as good as a DB-8...probably more like a DB4. I'm going to add another iteration to the motif and retest. The current antenna fits in a 49 sq in area, but is about to get bigger, significantly bigger unfortunately. There is no balun...drives 75 Ohm cable directly. I'll take a pic of it before I add another iteration. Lets keep our fingers crossed, for everyone's benefit.

[maximzodal]

So, have you had a chance to retest the "another iteration"? Would love to see a photo. Enjoy your and Williamruckman's repartee. I think I'm learning a lot. Maybe enough to be dangerous. Max

[HoldOnTight]

Maximzodal, I have done another iteration. It improved local UHF low channels significantly (as expected), but I don't think this will be needed after June 08! Also, unexpectedly, the bad side is a reduction of gain at the Higher UHF end of the digital band at a frequency of my interest. Maybe it is just a small bandwidth detuning effect brought about by the added iteration, which is typical of fractals. The pattern has been iterated enough to cover the high UHF channels. So the answer may be to scale the entire fractal slightly to move that dip in gain off of one of my desirable high-uhf channels. Hard to say without antenna analysis model.

I've been looking into different antenna analysis models. It has taken quite a bit of time to research this, pros and cons of each, how to model this antenna... Fractal antennas are a different beast, when it comes to modeling and analysis using the existing software tools. Also, I'm finding that due to the bandwidth, I may have to break down the antenna model into a more simplistic form, then gradually build it up to more of the current version and extrapolate the effects to see if my design is optimal for the Hi VHF and UHF digital band. These antennas can realistically have a size reduction of 10:1 on up to 1000:1 over the old antenna design paradigm. Antenna modeling is needed because the bandwidth range is wide and size reductions may be possible, and then employ multiple patterns to really pull in the signals, like the DB2, DB4 and DB8 versions. Meanwhile, I'm freewheeling and I've got 2 additional patters that I want to try/model. These could be even better! BUT FIRST: Thanks to RVogel for his novel approach of a bunch of nails to make the wire snake exactly to the desired pattern. That is a great prototyping approach. I'm going to build the other 2 types of antennas and test. Trying things, and analyzing the effects helps me understand how to improve further...

VERY IMPORTANT: Also, a fractal design is very good, but not optimal...another reason to analyze the antenna via a model.

If you are really itching to try something different, RVogel's approach should be a winner too.

[LittleRose~68]

I found an interesting fractal that I had read that is used as an antenna in cell phones and...well, here's a link. Maybe this design could work with this type of set up?

[HoldOnTight]

Hmmm, I don't see the link. Are you talking about a Sierpinski Triangle? Cobbling one of those together with wire could be challenging, but I am sure it would be effective. The best approach then, would be to print it on a circuit board and not a manual wire bending and soldering approach.

[LittleRose~68]

Here's a picture of the fractal I mentioned. I tried it using copper wire and connected it to the box using a coaxal cable. Mine ended up being about a foot across. The results were better than I expected. The UHF and the UHF ended up coming about the same and much clearer than with my amplified antenna. I may try to make it with more sides to make it a cube. I hate to have to find the exact placement of the thing as it becomes tiresome. I did tape it to a piece of cardboard and when it was sandwiched between two pieces, it seemed to work even better.

[LittleRose~68]

(removed by author or community request)

[williamruckman]

No, i haven't had time unfortunately. I also want to test it on FM/AM radio reception.

[williamruckman]

You should test it with the impedance matching transformer.

[HoldOnTight]

The impedance varies with frequency somewhat but it is not too misbehaved for a Fractal antenna. An approach it to connect to the antenna at a point where the impedance is 75 ohms, but the antenna design would need to be analyzed by computer, which is way beyond the effort I want for one antenna that I will not patent. Secondly, it may be impractical to interconnet the needed connection points, if the distance is extensive > 1/2 in. -- likely the case for my design. The idea is to make an antenna that is available for the average-joe to assemble from an instructable. Impedance and hence, VSWR are tolerable... VSWR is reasonable for Fractal elements, typically driven by a 50 ohm load. Fractal elements, according to Cohen have an impedance of about 30 ohms. So, I concede that 75 ohms is a less desirable match, but a balun really wouldn't help since a balun transforms 4:1 and the VSWR would be about the same, with or without a balun. It is possible to build low impedance transformer, with a 2:1 but problematic for HDTV. First, these often are limited in bandwidth and second, building one with the not so common materials is well beyond the capabilities of 99.9% of instructables viewers. What matters, from my point of view is not reflections, since HDTVs are resistant to some interference with digital processing -- there is no ghosting. I want raw gain to pull in those distant, but desirable signals that originate 50+ miles away. So, if the wide-band antenna doesn't quite meet my gain goal, which is rather lofty, then an antenna amplifier will help pull in the weaker ones so long as the amplifier is as close as possible to the antenna. The Fractal antennas can be made wideband to cover the desired spectrum, and that is their forte, as are the bowtie designs. The problem with building a multi-element (Fractal element) antenna is that it becomes physically large to reach the desired gain. But that isn't much good if the antenna is hidden in the attic and then you've got to run 50, 80 or 100 feet to get to the TV. I want an antenna that doesn't have to be hidden in an attic -- signal losses in coax are terribly high for higher UHF signals. I think it is possible to build something reasonably small and artistically pleasing or at least easily hidden behind the TV. That said, have you got your next iteration figured out yet? Time to bend metal!! ;) Bottom line, No Balun!

[bobneumann]

Would a 1:1 balun be appropriate here? I recently found a link to how to make a 1:1 balun from nothing more than 2 differing lengths of RG6 or RG59. I tried it and it seemed to work fine. I only did it because I'm too cheap to go buy the one from Radio Shack! But ulitmately this antenna is about the right impedance, but unbalanced. Right?

[williamruckman]

The length of the coax can attenuate your signal. Shorter and more shielded the better. RG-6 is always best and using higher quality fittings that are tightened down well will help. A 1:1 balun isn't needed. Typically dipole antennas have an impedance around 300 ohms but fractal antennas tend to be a little more than half of that. usually 150-180 ohms but that also depends on frequency. You would have to do some pretty in-depth mathematics to calculate it. I find it easier to just experiment and find what gives better results through trial and error. The balun I am using is a 4:1, but maybe you would have better results with a 2:1. But again, it would work best at your dipoles center frequency and since it is a fractal it would also resonate well at some higher frequencies as well. Which ever way you decide to go, let us all know your results.

[HoldOnTight]

A 1:1 coax balun isn't needed and may degrade performance unnecessarily. I'm a little rusty, but I believe the 1:1 balun, using coax cable, is frequency dependent and works only for a given wavelength. The length of the coax is determined by the frequency, correct? Insofar as your initial testing, you would need to compare the utility of the balun with the range of frequencies for your channels to the same setup without the balun. Maybe your stronger signals are strong enough to overcome the attenuation brought on by the tuned frequency aspect of the 1:1 balun. Use of RG-6 would be best for a UHF, to minimize the losses. The next time I buy coax, you can bet it will be RG-6. I'm not a fan of any radio shuck stuff...seems to be on the edge of poor quality, btw.

[williamruckman]

You could add a variable inductor or capacitor to change the inductance to see if your signal improves at lower or higher impedance values. Good luck on your endeavor.

[HoldOnTight]

Williamruckman: Yes, but as I alluded to, that would be optimal for one frequency and degrade much more with other frequencies in the UHF band.

[edx111]

How about making/designing fractal antennas for hidden transmitting antenna work for, say, the 11 meter band. any design info?

[williamruckman]

If you wanted a dipole for 11 meter transmission, you would calculate your dipole size to be a half wave across and quarter wave per leg. then take that length and bend it to the shape of the fractal. Here is the dipole design I used:

http://www.scienceprog.com/fractal-antenna-constructions/

Mine is a second iteration of this fractal, but I eventually will make this with a third iteration and test it to see if there is any improvement.

[torptorp]

If you go to the next interation of that fractal what would be the length you would use for each fractal. same legnth as 1 iteration 8" or must you use the same design with the 2nd iteration which would come to a length of about 10-5/8"? Just curious because I am about to try a 2nd iteration version.

[williamruckman]

The length would still be 8", you will have to make more smaller bends which requires finer tools. With each iteration, your bends occur at 25% of the previous iterations sections.

[Trailblazer1]

Hi, Thanks for your Instructable its very interesting and really grabbed my attention. I'm the process of building your antenna and have some questions. 1. Regarding gain, I think I understand you are using quarter wave length. If so, would using a half wave length or even a full wave length give any more gain, and maybe pull in a weaker signal? 2. What about building two and coupling them together? 3. Someone was asking about increasing the covered band width. Could that be done by using two different antenna's. One calculated to cover the lower end, and the other to cover higher end, but still in the same band width, and overlapping a bit, and then coupled together? Thanks.

[Woodie49]

Do you need one for each TV? Thanks

[williamruckman]

It would be best to use one for each TV. You could split the 75 ohm coax but you will loose 3.5dB each time it is halved. You would wind up needing a amp to drive more TVs.

[Osprey101]

Thanks for the great guide, William! I just built my own and it works just as fantastically as everyone says. I went from pretty much zero signal strength to full strength.

Instead of buying a backplate from Radio Shack, I used an inch-wide piece of wood (taken from a heavy-duty paint stirrer). I also introduced washers to make the contacts easier to screw together and so that I didn't have to bend the rails. Now that I know that the design works so well, I may create a wider backplate out of wood so that the wires can't poke things, but this one is so cute that maybe I'll just leave it.

BTW, I had a few baluns/transformers from the 80s lying around, but they didn't work so well. A brand new one worked great, though. So, if you use an old one and are less than impressed, buy and try a new one instead of thinking that it's the design.

Below is a photo and here's a link to a larger version to the image:
http://www.netfresco.com/FractalAntenna.jpg

[Osprey101]

I should also add that I made great use of the PDF template that the tutorial on your website provides. I hope that you don't mind that I link to it here, so that those following the instructions at this site can print out the template and use it: http://ruckman.net/blog/request.php?2

After printing that out, it was really easy to drill the holes and bend the wires at the right locations and at the right angles.

Also, if anyone is wondering, that's a mini zip tie that I added to secure the balun/transformer.

[charliefreck]

nice info. i did some research on the topic to make one well tuned for my desired frequency. i think you may be wrong about using 1/4 wavelength of wire for the elements. i believe it should be 2/3 of the wavelength. you thought you were making a koch fractal dipole, but your elements are not the same shape as the the second iteration of that antenna. you are missing the bits on each end. the shape you made can be thought of as an open koch delta loop, a loop antenna resonates at a wavelength equal to its circumference. an element bent 60 deg in the middle is 2/3 of the delta loop, and that is what you start with. a "rabbit ears" dipole is optimal when both elements are on the same plane in two dimensions.(pointing directly away from each other) they are essentially 1/4 of an open quad loop (square) antenna. as you move the elements into a "v" shape they become 2/3 of an open loop delta (triangle) antenna, and thus resonate at a higher frequency. i am new to this, and may have gone wrong somewhere. i would like to hear your thoughts.

[williamruckman]

I am always open. I guess my question would be is where did you find this information, and what is the math behind it?

[charliefreck]

i think i made some of it up. that pdf you linked to on your site is good info. wikipedia has some good articles. i think i may not completely understand the relation between dipole and loop antennae. i will do some more research and make some more antennae. at any rate, these work great. your guide is one of the best i've found on the topic. thanks.

[iac]

Dude greate ible I plan on trying for moms dtv. Even though she lives closer to ants than I do, a boosted rabbit ear& circle only picks up 2 digi channs; while I get all chans with an old pair of ears. Big question for you. As i said my old ears pickup all channs well except one UHF which is always spotty. Can anything be added to ears ( wire,foil ) to boost that one chann reception ? thanks IAC.

[nathenial]

what is the trick to maximising signal strangth, is it more acute bends or less obtuse bends, and can i add more then just two of these fractal shapes on either side, would that increase reception

[williamruckman]

acute or obtuse doesn't matter as long as it is a fractal shape. the fractal shape itself doesn't give you more gain at the center frequency but does give you a wider receive bandwidth at the cost of slightly lowering your center frequency gain. It is a trade off but well worth it for stability across the spectrum. This antenna design is based of dipoles, and with dipoles more elements means more gain. You could increase your gain by adding more elements but it will increase the total size of the antenna. But...it will still be smaller than a normal dipole of the same frequency.

[dfun47]

I'm gonna build this, as I've had poor results with my current UHF-VHF (in-attic) amplified antenna getting usable HD signals. A couple of questions. First, In step 1 it appears that the lid that you mount the fractals on is smaller that the box; is that just an illusion? 2) I assume the fractal connections should be isolated from the ground plane, is that right? 3) Is the ground plane aluminum Sheet or foil, how thick? 4) Is there an affect of fractal plane -to- ground plane spacing? what did you use? and lastly, 5) Should the fractals extend beyond the ground plane , or visa-versa, by how much?

[flerb]

I made 3 of these (so Far) out ov DVD video boxes and clothes hanger wire. My signal strength (by the coverter box meter) is able to hit 100% in VHF and pretty Good in the lower UHF Band. I have noticed the drop off in the upper UHF bands also, but it is still as good as the VHF/UHF amplified antenna I was using for upper UHF, and much better in VHF. I have tried to read all the comments, but couldn't find an answer to this question: If you want to improve the middle to upper UHF (channel 40 on up) which would work Better- (a) larger elements,such as with 2 inch lengths; (b) shorter length than 1 inch between bends or (c) a non fractal clothes hangar type with V shaped elements? (I live in a basement wherre people above also affect the signal, and again, that is most problematic on UHF)

[Xial]

Out of curiosity... I notice that you use a plastic box for holding this. If I were to use a metal box, such as an Altoids tin (of which I've got about 28 of them), would the tin affect the reception of signal negatively? My interest stems from wanting to make something that's a bit more compact than the current design.

[jonton]

i just want to say that if you need to, you can use coat hangers and bump it up to 2 inches in between bends. this is amazing how well it works and all from parts in the closet. try it because you are ganna wish you kept the reciept from that $40 antenna you bought that didnt get you squat for reception

[socrateez]

I built this and it works better than my amplified rabbit ears and uhf combo from Phillips. I live in an apartment downstairs surrounded by other taller buildings and large tall trees. I get a reflected signal off a nearby small mountain. My antenna has to point at it and not the transmitter location. I cant even get satellite. My signal fades if a neighbor walks around in their apartment. This works really well I must say. In a bedroom I have the same thing only not a fractal, just two bowties. It doesnt work nearly as well and seems narrower in bandwidth over the fractal as ive swapped them. I also tried rabbit ears paired to this with a transformer. In my case, I always get best results with the dipoles directed toward the signal source at a 45 degree angle. Thanx for this Instructable! Thanks for all the helpful comments too everyone. :-)

[HoldOnTight]

A BIG THANKS!!! to williamruckman for starting this ible thread! I believe this is the defacto DTV antenna ible to date! Good On YOU...williamruckman!

[williamruckman]

Thank you all for being so active and adding your own content!

[tmadore]

there's only one thing wrong that I see.. its that the measurements of the angles on the antennas are a combination of 120 and 60 degree angles, not all 60 degree angles..

[rturpin]

I combined the now famous "coat hanger" DTV antenna (4-phase bow tie) idea with the fractal antenna pattern and am getting very good reception. The resulting antenna is a good bit smaller than the coat hanger model, and reception appears to be as good or better. Have added a diagram.

[mickydean]

I, too, put this together with coat hangers, piece of wood...however I was not as successful as bytes2go... with an analogue tv I get much better reception with rabbit ears...is this design only suitable for digital broadcast?...also- I just read that a hdtv will not broadcast in hd without the use of a hdmi cable, true? I was thinking a purchasing a new lcd hdtv and would like to rid myself of my cable service and go with an "over the air" antenna such as yours- is there a transformer that accepts hdmi cables? thanks for the help...

[williamruckman]

This antenna also works on analog. You can get HD on a HDTV without HDMI cables. The digital tuner will be built in. Although, if you want to hook up an external HD device such as a PS3 then you will need an HDMI cable for that. If you want to use an older VCR or something, it will work fine but most people get an upconverter so the signal matches their native resolution. Although, I always go with the theory of crap in, crap out. If you want good quality out you need good quality in.

[beefaroni]

the biggest plastic project enclosure that they have in stock at my local radio shack was 7x5x3. does it matter it the antenna hangs over or not. fyi: im making your antenna this weekend. i'll tell you how it goes.

[williamruckman]

If you use a third iteration of the fractal it should fit perfectly.

[bytes2go]

Threw this together from some coat hangers, wire, screws & a piece of wood, amazing how well it works !!! Can now get stations I could not before... Thanks for the research & simple, but effective and easy to construct design.

[Vomish]

I was looking at the site you linked from your homepage (Television Frequency Table) and I am wondering why you used the CATV frequencies chart as opposed to the UHF frequencies chart? The CATV chart lists channel 45 at 350 MHz but the UHF chart shows the same channel at about 660 MHz. BTW, I have built this antenna and am getting excellent results.

[williamruckman]

Yes that is a CTV chart. Most TV charts don't display the new DTV / HDTV frequencies which is usually UHF. But antennaweb.org does. Try that one.

[Vomish]

You didn't answer my question which was why use CATV frequencies as opposed to UHF frequencies in your calculations (seeing that most DTV is located in the UHF band with the exception of some areas where the VHF band is used as well)? BTW, this is an excellent instructable that has got me obsessing over fractal antennas. Thanks!

[williamruckman]

I just looked at it again. It has both charts in it. UHF and VHF as well as CATV.

[Vomish]

You are missing my question. You referenced using 350MHz to calculate the wavelength: "350Mhz - 8 inch quarter wave - 16 inch half wave - which falls in the Hyper Band - between channel 1 and 90 which is a channel 45 center frequency for best resonance" In the UHF band, channel 45 is 660MHz not 350MHz (350MHz is in the CATV frequency range). So, why do you use 350MHz (CATV) instead of 660MHz (UHF) in your wavelength calculation?

[ste5442]

Doh!

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[williamruckman]

OK, I have fixed it up. It now reads: "(350Mhz - 8 inch quarter wave - 16 inch half wave - which falls in the Super Band - between channel 13 and 14 which is a center frequency between the VHF and UHF band for best resonance)"

[servant74]

I know that cell phones often use fractal antenna and I was wondering what the sizes of leads (actually the length between bends) need to be to make one tuned for the digital broadcast TV bands. Would anything be gained by making some additional bends thus making smaller replication in the fractal? Actually doing this on a printed circuit board, one could get some very fine traces, and it would be 'easily' reproduced.

[HoldOnTight]

Yes, but only up to a point. Beyond a 3rd or 4th iteration is impractical to make unless you have really good Printed Circuit Board capabilities.

[ste5442]

It should be easy to replicate a number of times on PCB - its nothing more than copper traces after all.
Fractus do not use any special methods for designing their fractal antennas although they do maintain (or license - cant remember!) a patent on the idea of an antenna made from a fractal structure.
I guess you could even make the author's antenna out of copper tape on bare FR4 if you had no etching materials.

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[mikedoth]

Can someone please explain how the the shape and size affects things? I'm new to EM Waves.

[ste5442]

In reality a dipole or monopole will give the best gain - the only thing a fractal antenna has going for it is size and a possible increase in bandwidth (at the expense of gain).<br/>Fractal antennas have been used for some time and there are patents on the idea (check out a company called Fractus) - the datasheets all show highly negative gain compared to an isotropic antenna ie. -dBi.<br/>That said, its a nice project and nobody likes huge antennas! If we all stuck to monopoles then our mobiles etc would look comical!<br/><br/>Thanks for the instructable - a gain figure would be great though ;-)<br/><br/><a rel="nofollow" href="http://www.pcbpolice.com/">PCB Police Electronics Forum - Try our competition!</a><br/>

[williamruckman]

This Nova video that prompted me to start this design may help answer your question. They start talking about the fractal antennas a little after the halfway point:

http://www.pbs.org/wgbh/nova/programs/ht/tm/3514.html?site=34&pl=wmp&rate=hi&ch=3

[HoldOnTight]

In laymans' terms, a particular shape optimizes the ability to pull in ALL of the available signal without reflecting part of it (lost signal).

[ste5442]

A particular shape which typically the same as the transmitting antenna....which is not a fractal or folded dipole. Anything less than the 'same' as the TX antenna will mean less signal at the receiving end :-(
Its a fact determined by the physics unfortunately.
Fractal antennas are smaller and 'can' have an increase in bandwidth - they have less gain compared to their monopole/dipole counterparts though ;-)

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[HoldOnTight]

I hear what you are saying, but it is important to compare similar beamwidths, similar bandwidths and antenna gain when comparing antennas in order to arrive at an apples to apples comparison. When you need good performance in all three dimensions, then there isn't much competition. The fractal antennas used in cell phones provide improved performance, and physically small, so that is why they are so widespread today.

If you really don't mind a larger size antenna, then you can go with something like this to really pull in the weak signals:

• Single Bay Gray-Hoverman (SBGH) for nearby to fringe reception range (approx. > 0 to 100 km or > 0 to 60 mi)

o Two Variants of the SBGH: with 6 Pair Collinear rod reflectors
o with 30 x 40 Split-Screen Reflector

OR,

• Double Bay Gray-Hoverman (DBGH) for fringe to deepest fringe reception range (approx. 30 to > 160 km or 20 to > 100 mi)

o Two Variants of the DBGH: with 11 Pair Collinear rod reflectors
o with 30 x 75 Full-Screen Reflector
Both can be found at: http://www.digitalhome.ca/ota/superantenna/design.htm

[williamruckman]

I actually looked at these designs, but yes they are big and ugly and directional. Which means this big beast would have to be mounted on a motor to rotate it.

[HoldOnTight]

Perhaps you misunderstood me. I believe you are under the assumption that everyone is not too distant from transmitters, but this is not always the case. If someone is distant from the transmitters, they are likely to be desperate and the mini-DB-2 variant in this instructable couldn't cut it. They may be happy to get digital channels even if only from one direction -- the nearest city. It fills a niche for some. People should have access to what they need. So I offered the link to the DIY antenna. No antenna is an end-all be-all solution to everyone's situation.

[realistic101]

Thanks guys, my wife and I where thinking of buying an antenna as we do not watch it too often. Now, the nearest TV stations are about 45 to 70 miles away from our house, will this antenna provide enough strength for good reception. ( we live near one of the highest points in Ohio, ie. we are higher than the TV stations around us) Are amplifiers available and usable with this antenna to increase the signal? Sorry but I am a graduate of Mechanical Engineering (6-10 years in fabrication and machine design) and a recent MBA graduate, antennas aren't my forta.

[HoldOnTight]

Yes, give it a shot and let us know! :)

[williamruckman]

You may be able to get some of the closer stations but maybe not the furthest ones. Only way to know is to try it out. The furthest ones may work with a RF amplifier although I have never tried it.

[ste5442]

Hi,

Will you be designing an antenna amp to complement the antenna?
Nicely documented instructable by the way ;-)

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[RVogel]

Here is a design that I put together. I will try it out tonight to see how it works. It is 6.5"x6.5"x1/4" MDF with a bed of nails (brads) driven into it. I first printed out the paper template on a laser and xerox transfered it with acetone. I pre-drilled all the nail holes on the inside corners of each bend. Hammered nails in, did 3 courses of 3 conductor wire (326-DFV, 6502), soldered terminals, then connected the transformer. I'll use aluminum tape on the back for a reflector. I've included a paper template if anyone is interested in trying it. I have no idea how it will work.

[HoldOnTight]

You might try adjusting your reflector 1 -2 in from the fractal for best performance. I'm trying to avoid using a reflector to get more coverage from different directions, but this is what I've found works best for max. signal strength.

[williamruckman]

Make sure those wires are stripped bare. Hard to tell from the photo.

[maximzodal]

What an exceptionally great project! Can't wait to get my converter box. However, I guess I don't quite understand how insulation on the wire is going to attenuate the radio signal. Is the insulation partially or completely radio opaque? Thanks Max

[williamruckman]

The plastic over the wire can reflect and/or absorb some of the signal. It is best to have it bare. I assume it would affect higher frequencies more as they have trouble penetrating objects more than lower frequencies.

[RVogel]

No, didn't strip them. Would it make a big difference? Many antennas are enclosed in plastic housings of one form or another, so I figured that the insulation on the wires would be negligible. Tried it out this weekend. Seemed to work good. Your antenna appears to get a higher signal strength. Both get reception on every single channel. One is I have with my converter box is that the signal strength meter function seems to be a bit random. Sometimes it displays 0%, but all the channels are coming it. What would be a good way to test signal strength? Thanks again for the great Instructable! You've put a lot of work into all this and it is inspiring.

[williamruckman]

You may get slightly better results with the wire bare. I noticed that some DTV boxes take a minute to properly calculate the signal strength. They start at 0 and slowly work towards the actual number.

[HoldOnTight]

I agree. Some plastics can attenuate the signal, but you may not notice the difference until you try a bare copper configuration. BTW RVogel, how did your testing results come out? I'm curious to know what type of antenna you use as your baseline test, how many analog and digital channels you get clearly & without noize or pixelation, both with the old antenna and the new antenna. Also, could you provide a picture that zooms in on your feedpoint to the antenna? Thanks!

[-Spiff-]

Wow! This is great! I live in a wooded, rural neighborhood with rotten reception of analog signals, even with amplified rabbit ears. I was excited about the switch to DTV, rushed out to get a converter box, hooked it up with the same rabbit ears and received ... zero digital channels. Dismay. I found this Instructable and thought I'd give it a shot before investing more money in a commercial DTV antenna. Just to see if it would work before making it pretty, I only made the elements and dipoles and mounted them on a scrap piece of 2" x 4" (no reflector). When connected tonight, I picked up seven digital channels and more analog channels than I ever had before! I am thrilled at the results, so thanks much for the posting. One tip: instead of getting the 18-ga wire at Radio Shack, buy some 18/2 bell wire at Lowes for 24 cents/foot. You'll save a few bucks for what little wire you need.

[williamruckman]

I am happy that it is working so well for you. It is good to hear other peoples experiences as everyone has a different situation.

[captsomer]

Nice Instructible! Thank you. I built mine and did some testing. Based on my results, I wound up leaving the metal reflector plate off and mounting the antenna in a vertical position. It matched or improved the performance on every channel except one (it fell by 10%) of my amplified set of rabbit ears. If I get up and move the antenna around, I can improve that one channel but the rest fall off a bit. Overall, build this antenna and use it. Don't waste your $$ on a store bought one. This works great.

[jdtwelve12]

This is a good I'ble: clear, thorough, and with enough supporting information to whet the scientific appetite. Nice job. I'm using cable these days, but I have one or two old rabbit-ear antenni stashed with my cables and such. I expect they're about to become obsolete. Does anyone know of any good projects for turning these soon-to-be-scraps into something useful?

[JCLightning]

Try it on your FM radio.

[williamruckman]

I will give it a try and see how it performs on my radio. Kinda funny you say that, because I have no antenna on my radio!

[williamruckman]

Here is the link to the episode of Nova that inspired me to make this Instructable:

Nova - Hunting the Hidden Dimension

[lakingsfan]

This looks cool. I want to make one. Thanks for sharing this.

[RVogel]

Great results! I can't wait to see the RF amp.

[augur45]

OMG! YOU READ MY MIND! I've been researching antenna's with just such a project in mind. Thank you thank you thank you.

[jdtwelve12]

When you sense that an antenna expert is reading your mind, it might be time for the aluminum foil hat... :)

[augur45]

lol

[williamruckman]

I have posted my test results verses a store bought $50.00 Antenna:

http://ruckman.net/blog/news.php?item.22.4

Enjoy!

[RVogel]

Another question: Could the fractal shape be laid out on a board, finish nails placed on all the inside corners, and multiple loops of magnet wire going around the nails to trace the fractal pattern? Could this method be used to somehow construct a 3D fractal inside a box? Would that make it omni-directional? I don't even know what a 3D fratal would look like.

[williamruckman]

Not sure if it would work or not, but here are some pictures of 3D fractals:

[RVogel]

Ibuilt this antenna yesterday, but with a few mods. Instead of a project box I used an 8"x8"x1/4" piece of poplar. The fractal is on one side and the reflector is 2" aluminum tape on the other. Drilled a hole through the center for the transformer leads to snake through. I have two RCA converter boxs (DTA800) and only ever hooked up one using a $30 indoor antenna. I've struggled for 2 months with adjustments and re-scans to get 19 channels and about 25% signal strength. I set up the second converter last night with this antenna and got 19 channels (some different) and 35% signal on the first try. The strength was highest with the antenna horizontal (?) Some questions I have are: Can the antenna be scaled up? If so, in what fashion? And, could the antenna be made on cardboard using narrow copper-foil tape?

[williamruckman]

Some stations could come in better horizontal it just depends if they are transmitting with vertically or horizontally polarized signals. Yes, it can be scaled up and be adapted to other antenna models. Yes, you could make it on cardboard with foil tape ;)

[RVogel]

Here is the template.

[williamruckman]

Real nice! I bet this will help many people out.

[RVogel]

Nice instructable! I made a template pdf to try this out with. A paper template is always nice when bending wire, especially with angles.

[HoldOnTight]

I've been researching antennas, as many have. I've built a correct 4 bay bow tie antenna, commonly known here as a DB-8 antenna, decades ago, and just recently. It performs very well, and much better than the ones shown as HDTV antennas found on this domain. It is best on UHF channels and yet, there are 38 high-VHF channels in the US that will be transmitting DTV. Some really good ones are near me, so I am looking for a super-wideband design...no joy, yet! So I'm not posting the DB-8 instructable...but I include a hint below to help people fix theirs to work better and it will work with the williamruckman design!

Nonetheless, I am pursuing something smaller, wider bandwidth and more easily disguised so it doesn't have to be hidden in the attic. Fractal antennas are inherently small, so that has been my focus.

It has been difficult to find good information. I thank you for posting your instructable as it further motivated me to pursue something better.

For those unaware, Fractals can be used as reflective elements, ground planes, transmission lines and passive or active elements. According to Mr. Cohen, antennas have certain features to be a truly fractal antenna. What is presented above is a fractal element modification of a 2-bay bowtie (AKA DB-2).

I believe you will get better performance if you have elements that are spaced using the repeatable pattern (motif) or at least a 7 in. bow tie spacing, rather than 4!. What you do have is a balanced arrangement of "low order" fractal elements. As I understand it from reading, the bandwidth of your antenna design is still rather narrow (1-2%) around multiple frequencies as it doesn't implement more than one iteration of the pattern. As a result I believe this antenna has impedance mismatches and undesirable beam patterns and poor gain and bandwidth relative to it's potential.

Unfortunately, other HDTV designs on this site are also lacking the peak performance they are capable. Maybe some more people will chime in on how this fractal element DB-2 variant performs as compared to their other common antennas (such as the, dare I say it, 7 in. diameter loop antenna -- that really is narrow bandwidth for it's center frequency and poor radiation resistance. Unfortunately now many people have compared how many digital channels the williamruckmand design gets as compared to the more common antennas (same pointing angle for apples to apples comparison).

The great things about your instructable is that:
First, it gets people trying things -- me included!
Second, it also has lots of references that lead people to additional information.
Third, using fractal elements on an older design is innovative! :)
Fourth, it motivates me to make a higher order fractal design that addresses some of the goals I mentioned at the start.
GOOD ON YOU!
Hopefully, I can post my own instructable soon, but first, I have some building and testing to do. :))

[williamruckman]

WOW! Nice post! I agree with everything you said. You are well informed. This is my first DB-2 design. I do plan to refine it and make it better and your tips are spot on. I also planned to try this design with a 3rd iteration of the fractal as this one is only a second iteration. It is funny you mentioned the DB-8 design because that is going to be my next design and I am going to use the fractal design with that as well. I agree that it would have better gain as it has more stacked elements. Good luck! And I am glad I could be of assistance!

[HoldOnTight]

Okay, spent today figuring out the details of the new design. I tested it, but it isn't as good as a DB-8...probably more like a DB4. I'm going to add another iteration to the motif and retest. The current antenna fits in a 49 sq in area, but is about to get bigger, significantly bigger unfortunately. There is no balun...drives 75 Ohm cable directly. I'll take a pic of it before I add another iteration. Lets keep our fingers crossed, for everyone's benefit.

[RetroTechno]

When you say "20% more efficient than normal antennas" just which antenna do you mean? Do you mean a passive half-wave dipole? A yagi? An active antenna? That's quite a broad generalization to make. Cool instructable. I'm going to read the background info now. Thanks!

[static]

The problem is that efficient is undefined. I'm skeptical that a dipole shaped in to a fractal can be anymore efficient than a conventionally shaped dipole, until I'm shown antenna range data. In the event efficient means that fractal shapes permit better array to be built in smaller space, that I can understand.

[williamruckman]

I am really busy currently but I eventually plan to get some signal strength comparisons from my custom build verses a store bought amplified 50$ unit.

[williamruckman]

20% is a general number that has been found among many designs but it does vary. I used a dipole design with mine and I chose a fractal shape that would go well with that. Other fractals would be better suited for different types of antennas. For instance if you wanted a loop antenna you might prefer a snowflake fractal as it is a loop shape.

[webman3802]

So if the most efficient orientation for a VHF dipole is perpendicular to the broadast source, then the fractal design ensures that at least part of the antenna is oriented, maybe not perpendicular, but close, no matter what the direction of the source. How would you design one to also pick up UHF signals? Also, would it be possible to design the reflector around the same principles? Instead of one large sheet that would reflect from one general direction, you could have multiple small reflectors arranged in a spherical pattern, spaced apart to allow the signal through, but it would be reflected by the inside back to the antenna core.

[williamruckman]

This antenna also picks up UHF signals. It does both.

[mje]

Actually, a receiving antenna should have the same polarization as the transmitting antenna, or it will suffer a very large drop in signal strength. HDTV signals are horizontally polarized, so this antenna should have the elements rotated 90 degrees from the way it's pictured.

[williamruckman]

I agree. The bottom of this antenna is where I have the transformer sticking out. I will add that info to the walkthrough. Good catch!

[williamruckman]

I think those are good ideas! Basically, the best way I found to build them by hand is to take a current antenna design and then find the best fitting fractal for the antennas components. As I said in some of the other comments, i think the reflector could be more useful if made more directional by using a parabolic design like a satellite dish only made to fit the fractal design.

[arubajack]

I have a situation where I need to build this fractal antennae but also need to convert the new digital signals coming in(as of feb.) to my old tv that doesn't have a digital tuner. Is there a cheap way that I could build a digital tuner for uhf signals and not have to buy an $80 converter box?

[static]

But you got to consider what you are getting for your 80 bucks, less if you ordered your coupons. Your getting a fairly powerful computer, not to mention the associated RF circuitry. A universal remote come in the package too.

[williamruckman]

only cost about 80$ if you go with a SDTV unit, but it will cost more than a 100$ for a HDTV unit. The government coupons help but they are out of funding for that now.

[williamruckman]

I don't think so...

[webman3802]

Something to this effect, but having more than three reflectors (simplified example). Gaps are arranged opposite the reflectors to allow the signal to pass through, then get reflected back to the antenna.

[mje]

In your diagram, as the reflector size increases, you lose aperture and create nulls. You can't get gain this way. The way to get gain in an omnidirectional antenna is to stack elements vertically, which results in a narrowing of the pattern.

[williamruckman]

Not sure how well it will work, but there is only one way to tell ;) The design I was thinking of was kinda inverted compared to this one. You have the antenna inside the reflectors and I was thinking of the antenna outside the reflectors. I am sure both will work. Now I am curious about your idea as well.

[gahrere]

Hi Bill,I have some few questions. First can I use aluminium wire instead of hookup wire? Second is there any contact between the reflector and the hookup wire? Third should the tips of the hookup wire extend more than the size of the 8x4 plate? Thanx buddy.

[williamruckman]

yes, you can use aluminum wire as well. The more conductive a wire the better. You could make it out of gold ;)

[knowonesreal]

well it worked 4 me....i only get 1 channel with it but it works......(where as b4 i couldnt even get a signal with rabbit ears) the 60degrees angles were the hard part....... do u think this could be used in a 3d type..? not flat on a box as it is.....but on a ball...cuz ive got an old hamster ball lying around...lol

[williamruckman]

You may have luck with that hamster ball if you put a snowflake fractal around the outside and shape it as a loop antenna. Then put a parabolic shaped dish on the inside with the fractal as the focal point. I would try and make it with the cardboard inserts from paper towels cut in half and tape aluminum foil to them.

[mje]

Rather than a parabolic reflector, which would have to me much bigger than the antenna to be effective, try using a flat reflector about 4" behind the antenna. This should double the gain. The most effective way to increase gain beyond a reflector and more elelements is of course more altitude.

[williamruckman]

True, one big point to use fractals is the benefit of size decrease which would be counterproductive with a parabolic dish.

[williamruckman]

It is good to hear that it is a improvement over what you had. This model is pretty directional. Usually the best place to mount antennas is in your attic or outside but this one needs to be aimed by hand unless you modify it. If you can, try and move it about seven feet up and away from the TV or electronics. You can get interference from them that could be causing some problems. I am currently looking at making a omnidirectional unit. But I haven't hashed the plans out yet.

[KC0GRN]

Oddly enough I went to Radio Shack last night to pick up supplies and they didn't have the right sized box, but I got one fairly close (7x5xI forget). I'd be interested in seeing what you come up with for an omnidirectional, as I'm trying to design an antenna for my girlfriend. She's a long haul trucker, and constantly has problems with signal reception on the road. With analog, you could usually get something in, but now with digital, it's all or nothing. Obviously, designing a good antenna for a truck is going to be a challenge.

[williamruckman]

One of the issues I see with digital is that you have to scan the frequencies to see what is available which could be difficult in a truck if it is moving. You may need to stop and scan first to acquire a station. With analog this wasn't as big of a problem. If you knew what was in your area first you should be able to change directly to the best stations.

Here is a good web site for finding stations and antenna types per area:

http://www.antennaweb.org/aw/welcome.aspx

What would be nice is if you could couple antennaweb.org with a GPS and google maps so you could see the distance, channel, and compass direction from the truck while you were moving on a map. :)

[KC0GRN]

Actually, she has an RCA converter box (the DTA809, not the DTA800s available at walmart), it has the capability of scanning and adding channels to it's currently saved list. That is the one lacking component of some digital receivers though, the inablility to manually add a channel, like you can on just about every old tv. Thanks for the site, I knew about it already and have been using it for figuring out channels on the road. The sad truth seems to be the familiar cliff effect on digital (all or nothing) is very pronounced, especially in weaker signal areas. I know antennas can only do so much to cure the problem, but it's about the only thing the consumer can do, besides amplifiers. Still, I guess it's just a lot of trial and error to find something that works. The nice thing about fractals in a truck environment is saving space though, definitely an advantage.

[germeten]

Hi; excuse me, but did you say this fractal design only fetches ONE channel? I was searching for DTV antenna designs on youtube and in one of the comment areas, a guy said to take a straightened coat-hanger, wrap around a coffee can, then expand the loop to 7" dia. ;use a needle-nose to create screw terminals on both ends, then attach a 300/75 ohm balun. I attached to an inverted yoghurt container as a stand, using a converter box, am picking up 20 local (Milwaukee/chicago area) stations, a friend in the same bldg. is getting 24. It really is that simple and yes, it is directional.

[williamruckman]

This design works for all TV channels not just one.

[phip]

Wonderful! It would be neat to adapt this to WIFI 802.11 signals -- would that be as simple as calculating for a different center frequency, or would there be more to it than that?

[f 451]

Built this thing in 20 minutes from scraps. Works amazingly well.

[sr1sws]

As Spock would say, "Fascinating" ;-) Are fractal antennas also suitable for transmitting? I assume so since you implied use for WiFi. Any info on constructing an unbalanced version? E.g. for potential use with WiFi or MURS (close to Ham 2 meter band). Any info on designing for an arbitrary frequency band? Inquiring minds want to know! Steve

[williamruckman]

Yes, fractals can be used for transmitting. You just have to make sure that the wire you choose can handle the power output. In fact, the first fractal antenna was used for ham radio in an apartment. The apartment complex wouldn't let him put up a ham antenna because of the space limitations and then the fractal antenna was born.

[laernmoer]

I appreciate the idea and execution of your instructable, it is easy to follow, but I'm a little skeptical about your antenna - it doesn't look like you calculated for any particular frequency, and bent wires into a partial star shape. Can you please link to your source or add references for determining the wire length, angles used and gauge selection? I've worked with RF systems before and have never seen this before, although they were much higher frequencies than HDTV signals. This is nitpicking and minor but, I'm also confused about the "fractal shape" It doesn't look a fractal to me...

[laernmoer]

Ok, sorry, I found your links - they're in your original post on your web page. What sort of improvements did you find? Did this work better than using an antenna on the roof? (oh and I see now the fractal shape from your web page)

[williamruckman]

My original webpage ruckman.net has a lot of the design theory on it. This is just a step by step on how to make what I made.

[knowonesreal]

question about the reflector box.....its just Aluminum lid...do the self setting screws go into it? and how thick is this Aluminum lid..? i ask about the screws cuz in gonna make1.... and i ask about the thickness cuz i could just use a soda can(or 3 or 4 or 5 laid together)...and just place that into one of the many empty baby wipe boz we have around the house....lol

[williamruckman]

the reflector is completely separate and not connected to the main unit via a conductive material. The thickness doesn't matter. You can use aluminium foil or even a wire mesh as a reflector.

[simplicity is key]

wow, impressive with a capital I.

[technick29]

Sounds wonderful. My house is plagued by poor over-the-air HD reception for some channels and it ruins movies and TV shows when the TV freezes from lack of signal. We've already tried out making our own antennae, one out of coathangers, and it worked pretty well. Unfortunately, it fell apart and we reverted to the old antennae. This compact antennae looks very attractive, especially with NFL playoff games. :D

[KC0GRN]

Interesting Antenna design, I'm going to have to experiment with it to see if I can create one that will maximise my tv reception. Thanks for the idea!!!

[geeklord]

cool, i saw a TV show (Nova?) on fractals, and they mentioned this.

[threecheersfornick]

Yes, Nova. I saw it too -- it was great. The bit about computer graphics was amazing.