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Picture of 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

Showcased in the March 2015 issue of Popular Science Magazine:

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

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

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

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

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

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

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

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

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

Wikipedia info:

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

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

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

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

Basic supplies (cost me about $15):

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

NOTE: The bottom of the antenna is to the right of this picture where the transformer sticks out.

 
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williamruckman (author) 2 years ago
I have made some new elements using a paper template I made in Gimp (photo editor). I used small solid core wire from telephone wire and it was solid enough, small enough, and malleable enough to bend into the intricate shape required at the selected center frequency (554Mhz - as this is the mean of the digital UHF over the air TV channels in my area) and iteration of the chosen fractal design. Which is repeated triangles.

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

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

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

Enjoy.
fractal.pngfractal.jpg
tg5690 made it!10 days ago

Understand this is an older project, but it was exactly what was required as it was time to cut the cable cord. Not only used parts of this plan but also incorporated the best of similar designs out there. I'm no expert, but have done enough tech builds to get the feel of what looks important in other designs. Ended up with a hybrid design that used both the small and large fractal shapes plus two sets of bow ties. Added the reflector and it works great! The big change in my shapes is that I filled in more of the interior so as to capture more signal with more surface area in my elements. Made a jig to help in the bending process - but with 8 gauge wire it was a tough process. Made it through with vise grips and pliers. Probably made some mistakes, but it works. Thanks to all who shared their hard work so the rest of us could copy and have fun with it.

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tg5690 tg569010 days ago

By the way, getting consistently great results from towers about 30-60 miles away and when the atmosphere is cooperating, actually got signals from about 200 miles away. This last only happens occasionally and not the normal performance of this design. Not bad for an attic mount. Since this is feeding multiple TVs, added a amplified splitter to compensate. In my initial tests without an amp, this fed 1 TV a strong signal on its own and got the occasional distant signals without the amp as well.

tg5690 tg56909 days ago

A few things other designers thought was important:

The moisture in wood conducts electricity so the main upright in this build is leftover decking material that is more plastic than wood fiber. Thought about some PVC lumber, but that stuff is expensive!

Another plan thought it important to maintain the spacing of the phase lines when they cross. My plan has half inch stand offs for the phase lines and a full one inch spacer where they cross. One line goes over and the other under to maintain that distance and presumably cuts some crosstalk.

One designer wanted 9 1/2 inches between the main elements, but I opted for 8 as my attic is a bit cramped for vertical space.

Read where different lengths of elements were better at different frequencies. I did not do much of the math. Frankly this build was more for fun and experimentation. Instead I decided to go with the hybrid approach as that would give me three very different lengths for the elements. I hoped that would provide a good range of frequencies. The lowest channel I get is 8 and have seen channel 61 on those rare nights when long distance signals come in.

Decided to use small carriage bolts to secure the elements to the phase lines.

If this were to be used outside, probably best to use aluminum and PVC for the framework as the wind would catch this and tear it up!

Drilled a hole so I could put the balun on the back. Don't know if this helps anything,but it allowed me to put a short coax line between the balun and the amplified splitter and mount the splitter on the back of the reflector.

tg5690 tg56902 hours ago

One more thing. Most plans that specified reflectors indicated the optimum distance between the elements and the reflector was 5 1/2 inches. Note: Reflectors make antennas highly directional, so try your build without the reflector first to find out if it is truly necessary. I used hardware cloth but others use aluminum foil, metal cooking grates, and thicker bar stock for the reflector material. The purpose of the reflector is to increase the signal strength so if your build needs just a bit more signal to clear up certain stations, this may be just the ticket. Also since the reflector makes the antenna directional you might need one if you live in an area where co-channel or adjacent channel interference is an issue. In my case, we have some adjacent channel interference between channels 30 and 31. Since both towers are both in the same direction, my reflector cannot assist and block one. Wonder why the FCC allowed this issue?

Can i see a bigger picture of your build ? I am trying to design an antenna that reaches at least 80 miles
tg5690 made it! kevincarruthers9 days ago

Here is a picture without the reflector. Hope this helps.

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tg5690 made it! tg56909 days ago

Here are the templates I used for the jigs. Each segment is one inch.

image.jpgimage.jpg
kevincarruthers made it!7 days ago

I kept mine the same size as my whisker antenna to compare them. This antenna does have better reception and it is only about 1/2 as wide as my other. As for bending the stars I simply made a pattern and used finishing nails on the corners to bend the wires. He bought antenna I have received 2 channels and this one receives all 8 of my local channels including ch10 (192mhz) 30 miles away. Now I'm trying to get the next station at 60 miles. Thanks for posting this and thanks to tg5690 for sharing your pic, I will be using some of it in my next build

20150823_072839.jpg20150823_075924.jpg

I recently built a 4 DP "whisker" antenna and it works better than expected, I can reach about 30 mi with it. It does currently get ch 10 (192 mhz) which is the local channel for us so I need to be able to get it. Now my question is this- the whiskers are 10" long so each wire is cut at 20" and bent to give me about 4" between each whisker tip. When I design my fractal antenna would I still cut the wires at 20" and bend them or does the fractal design create a longer wavelength because of all the bends? Also would I keep the closest points of the fractal antenna 4" apart? I tried using the antenna analyzing tool MMANA-GAL but as I am new to this I don't know how to use it properly

williamruckman (author) 1 month ago

Hello Everyone! I just wanted to drop in and let you all know a few things that happened with the project recently. I have attached a picture of a build I did on Plexiglas which is one more iteration smaller.

Also, this antenna was showcased in the March 2015 issue of Popular Science:

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

There are some more things in the making, but i will hit you with them when it is a reality!

Let's keep the wonderful collaboration going! I can't wait to see more of your designs!

CAM00012.jpg
gerry19462 years ago
OK I'll try this again.

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

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

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

Sorry if I get multiple images. ??????
Antenna 002.JPGIMGP0566.JPGAntenna 002.JPGIMGP0566.JPG
ku5e gerry19465 months ago

You want to design Antennas, I suggest you use a program like, MMANA-GAL to simulate it before you build it. http://hamsoft.ca/pages/mmana-gal.php
A couple of observations on your idea.
1. You have to be careful with the feedpoint impedance. Your TV equipment uses 75 Ohms. Most antennas, like the fractal and loop antenna I posted above will have a 300 Ohm feedpoint. This is the reason we use the adapter. More specifically a BalUn. In this case a 4:1 BalUn to convert 300 to 75.
2. Your design assumes that the feedpoint will be 75 Ohms, I guarantee it will not be. This is why you have to simulate it before you build it.
3. Antennas want to be balanced (in most cases), your design will be imbalanced so the feed point will have to be moved to achieve balance or a suitable feedpoint impedance.
If there is an impedance mismatch (antenna to receiver) the amount of signal present at the TV will be much lower.
For example if you connect the 75 Ohm coax directly to the feedpoint of the fractal antenna I posted (which has a 300 ohm impedance) you would experience 4.087 db loss. Every 3 dbs of loss is a halfing of the signal. Therefore, you would loose more than half your signal.
I hope this helps.

ghz24 ku5e1 month ago

Your statements are correct, but your math is wrong.

75 vs 300 ohms gives a SWR of 4 and a miss match loss of ~1.9 dB.

A SWR of 8 gives the ~4 dB loss you stated.

A point you didn't cover is that SWR of greater than 3 can interfere with the tuners ability to decode the digital symbols and resulting in a much higher apparent signal loss (signal quality ).

You are absolutely right about modeling and simulations.

AdrianC13 ku5e3 months ago

Hello,

I was wondering if you could help me out with a few doubts I have.

1. Is the design (like for example the one in this instructable) dependent on the location (city/country/continent)?

2. If it is, what details do I need to find out in order to design an efficient "HD" antenna (transmitted frequencies or other stuff maybe)? If so, any suggestions on how to look them up?

3. Do I need a BalUn regardless of the design of the fractal/antenna I make or is the design dictating if I really need it? I ask cause I found a "box" design in youtube where they basically just stapled the narrow end of the antenna to the coaxial, no balun, but then you mentioned that most antennas will need it.

Thank in advance for your help! :D

gerry.friso ku5e5 months ago

Thanks for your comments. I have moved on from the circular design. It did not work as well as the rectangular design. I built a larger (More Fractals) antenna which worked quite well but it was large and not very attractive.

ku5e gerry.friso5 months ago

Gerry, I am a HAM radio Extra class operator, and have studied antenna design a lot. My hobby relies on it very much. One thing that is not mentioned in this instructable, partly because it is out of the scope of it, is that even number of elements tend to work better. Keep that in mind when creating antennas. Also when you have stacked elements it is a good idea to have half of them out of phase to the others.
What this means is that if you call one wire A and the other B, have A going to the left side of two elements and then to the right side of the other 2 elements. You can see this in the design I posted a few days ago in this forum. Good luck and have fun experimenting. That is what it is all about!

The circular fractal antenna that you have showing in a diagram - did you make it yet? How did that work out?

chuckr446 months ago

Can't you paint this shape using liquid conductive paste?

ku5e chuckr445 months ago

You could, but it would be very thin. The thiness might limit the antennas bandwidth (frequency range). This antenna needs to receive from (470-698 Mhz) which is pretty wide.

ku5e made it!5 months ago

Here is my version 8 elements. After building it I found that I had poor reception in the HI-VHF (7-13 {174-216 Mhz} area. While there are not that many DTV channels that use this range, here in Orlando, Fl, one of the major channels is Channel 2 and it uses DTV Channel 11 (198-204 Mhz). The frequency is not quite UHF, in fact it is very much VHF. This Fractal antenna is designed as a great performer in the UHF range (470-698 Mhz), but not so much n the lower frequency range.
In order to remedy this I added a full wave loop designed around 195 Mhz, which also the center frequency of the HI-VHF range. I then connected it to the end of the phase lines. This works because at UHF frequencies the loops impedance is so high it does not effect (much) the UHF part of the antenna. And the same is true for the UHF's section impedance when using VHF frequencies.
I put it together and tested it and all the channels listed on antennaweb.org were viewable.
This antenna works almost as good as the huge Grey-Hoverman/Cat Whisters I presently use.
Pictures attached.
1. Antenna on my jig board
2. My design on paper with loop dimensions
3. My Cat Whisker Antenna

IMG_20150325_191306088.jpgIMG_20150325_192050832.jpgIMG_20150325_192208117.jpg
AnithaG19 months ago

hi friends,

Am going to do research in fractal antenna can anybody say what recent problem in fractal antenna? and how to find recent problems in fractal microstrip patch antenna?

davidbarcomb9 months ago

Very nice instructable, clear and concise.

AaronW310 months ago

I got a 6' coax for $4 and the transformer for $3 off of ebay, both shipping quickly from the US.

JeypiB11 months ago

I'm late reading this blog but I find it a good and helpful. I cant wait to do this It is a good thing I've read this <a href="http://rcaantennas.net">How to Install Antenna</a! I can't wait to do this!

burnerjack0111 months ago

Making a jig on a board using small nails or screws would make this go very quick and very repeatable. I can't wait to do this!

gemluvr1 year ago

Holy CRAP! This is COOL!!! I want to try and make this stuff! I'm finding it's answering questions I've had when reading all the posts. This is GOOD!!!

MrEggsalad made it!1 year ago

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

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Dalmo2 years ago
Hy guys! May I do the Fractals with 12AWG wire? Because this wire we have!
Txs
Peace
SpikeG792 years ago
Just made 2 of these 'fractal stars' design that is in ToriAmos' post to add to my original Ruckman design antenna and gained about 5-10% signal strength on all channels. Very impressed :). I added them to the screws that held the transformer terminals. The 5 major network channels now come in @ 80-100% from 70-90%. One new local lower powered station strength went from 50% - 65-70% and is now watchable. I made them with 20 inch lengths of coat hanger wire so there's about 1/2 inch between bends, they take up about 5 inch x 5 inch square area. If I would have made them 10"x10" square area you would need about 40 inches of wire and 1 inch between bends. Hope this info helps.
SpeakerBoy2 years ago
I've made a version of this using ¼" adhesive-backed copper foil tape (the kind used by stained-glass hobbyists) applied to a sheet of acrylic, (without a reflector) and the results were both beautiful (think "Copper Snowflake Sun-Catcher") and impressive. By printing out your template and lining it up with match lines I put on the backside of the acrylic sheet, I was able to apply my strips of foil directly over it in the appropriate places. The adhesive is NOT conductive, but a few well-placed needle pricks soon cured that problem. Once I found the "sweet spot" in my bedroom window, it was performing just as well as my Gray-Hoverman (with reflectors!) while taking up a fraction of the space. It's an elegant little solution for apartment dwellers! I can't thank you enough!
Foil.JPG
jschwab4 years ago
I've modified the design to increase fractals, adding another set of fractal "whiskers" giving 3 sets per side and iterating the fractal shape several more times, while still fitting into the same compact space.

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

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

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

Thanks,
Are there a couple of segments missing from the free end of each loop? It seems like there should be 5 small identical loops within each main loop. I have a modified version and would really appreciate it if someone could tell me if I have done it right.
for this design do you use all 6 fractals or could you use four like in this ible?
At what size should I print this template to achieve the same center channel as the one from the main instructable?
I printed mine at the default printer setting for a full 8.5 x 11 page. hope this helps.
So, does the image take up the whole page?
If you print with no scaling it should take up a little more than half the page. mine came out centered on the sheet of paper, with the longest edge measuring around 6 inches.
Thanks for the help, and thanks for an awesome Instrucable.
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