Instructables
Picture of Fractal Antennae
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Fractal Project Antenna.jpeg
Amelia and I Fractal Project.jpeg

Fractals are more than just intricate shapes and appealing pictures. They encompass our lives, appearing in places as tiny as blood vessels and as widespread as the patterns of tree branches. Yet, what is a fractal? Mathematically, a fractal is described as a curve or geometric figure, each part of which has the same statistical character as the whole.

As far as telecommunications, fractal-shaped antennas have greatly reduced the size and the weight of the antennas for a given frequency of use. Practical shrinkage of 2-4 times is realizable for acceptable performance, and has eliminated the need for the bulky antennas of the past.

However, fractal antennas plugged into HDTV televisions, or even other types with the aid of a converter box, can receive several local channels, free of charge and completely legal.Throughout our project, we will show you how to build your very own fractal antennas from three different materials.

 
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Step 1: Gathering Materials

Description of Total List of Materials Used

Small Roll of Lead-Free Solder (Most Effective)- (Quantity: 1)

Small Sheet of Plexiglas- 1/4" thickness (Quantity: 2)

Roll of Aluminum Wrap- (Quantity: 2)

Soldering Iron and Station- An individual Soldering Pen costs approximately half of the price of a Soldering Iron replete with a station. However, we used a soldering iron with the temperature station.

Wood (Squares)- Dependent on quality, but can be obtained for 38 cents per square foot. (Quantity 1)

Roll of Insulated Copper/Silver Wire- The cost is dependent on brand and quality. Non-insulated wire would be an option as well if it were thick enough. (Quantity: 1)

Small bag of Screws- (Quantity: 1)

Manila Folder- (Quantity: 2)

Graphing Paper- (Quantity: 2-4)

Stapler (Quantity: 1)

Pencil- (Quantity: 1)

Scissors- (Quantity: 1)

PhilKE3FL6 months ago

Very nice work ladies! I love it when someone your age does something like this.

You might try attaching the wire to the antenna at different locations and not always the same distance away from each other or an equal distance along each path. You might also include drawings as to where you attached the wires, either I missed them or they weren't included. The old bow tie UHF antenna is a very basic fractal in some ways I guess. A full-wave-loop antenna is very similar in look to your snowflake fractal. The way it is normally attached to the radio or TV is by breaking the loop at some point and attaching both wires from the radio or TV to those two end points, one end point and one wire. I have never seen the feed line (the wire going from the radio/TV to the antenna) attached at opposite ends of an antenna as you seem to have done with your snowflake fractal antenna. In this case you may have an antenna array and not a simple loop antenna. Also, with your feed line attached to opposite ends of the snowflake you have inadvertently used part of your feed line as part of the antenna, which changes things considerably. A feed line separated and stretched out is a form of dipole antenna. The most basic of all antennas is the half wave dipole, meaning that the length of the dipole antenna is one half the wavelength of the radio frequency you want to receive or transmit. Thus, the full-wave-loop is an antenna whose length is equal to one wavelength of the frequency of interest. With TV frequencies one can never design a single element antenna capable of receiving all the wanted frequencies equally. Your fractal antenna might be able to better manage this wide frequency range requirement.

As for the triangle antenna I'd like to know how you attached the wires to it. I may have to keep this around and try some tests on it as well.

If one were to take a full wave loop already attached to the feed line and un-loop it, it could be made to look like half of your snowflake fractal antenna so, I guess in a sense, you have two stretched out and somewhat bowed "loop" antennas attached to the feed line, that's a form of antenna array, two or more antennas attached in some way. Usually multiple antennas are attached together with a phasing harness. This harness is made of feed line of a very specific length and is called phasing the antennas because the length of the wire between the two or more antennas is cut so that the signals from all antennas come together with the same phase of the sine wave signal so that they add together, thus giving the receiver a stronger signal. There are ways to phase multiple antennas so that they add signals from specific directions and decrease signals from other directions as well.

You can see some of my work on TV antennas and tests I've done on my web site and on my forum.solidsignal.com blog. The antenna I've been studying is the ubiquitous bow tie with different element lengths, separation angles and even in the quad element arrangement. The "ultimate" design is for 360 degree reception of horizontal waves that my wife named the porcupine antenna. I called it the "quad element turnstile bow tie" antenna, her name is much better :)

A full wave loop antenna has a 300 ohm impedance and a dipole antenna has a 75 ohm impedance. Most TV antennas are designed for one or the other and then changed for the TV to use if needed. That is a complete story in and of itself with no easy answer either. Older TVs had 300 ohm inputs (usually using twin-lead wire) the new TVs have 75 ohm inputs and use 75 ohm coax cable.

Porcupine antenna photos: http://cs.yrex.com/ke3fl/Articles/Antennas/BuildingThePorcupine.htm

Links to my articles on SolidSignal.com at Karras' Corner: http://cs.yrex.com/ke3fl/KarrasCorner.htm

The specific articles of the bow tie (not the turnstile version) tests are called:

Bow Tie Element Length Evaluation

Transformer Tests

Bow Tie Antenna Angle Tests

and you might also look at the "The Standard Bow Tie Antenna" article.

Keep up the good work! It looks like the two of you had great fun doing all that.

alzie PhilKE3FL6 months ago

Cool project.

But, as ive found out with electrically small antennas,

Their coupling to the ether is compromised.

As such, their Q is increased, while their band width is reduced.

This is fine if youre not looking for a wide band antenna.

Not so good for UHF TV.

Then, there is the issue of matching.

Loops are higher Z and dipoles are lower Z than you realize.

When in doubt NEC it out!

I am not a engineer of any sort but AI have found the same thing that the aluminium antennas do not get all the stations. We have two different kinds of antennas and get quite a few more stations using both.

http://www.instructables.com/id/Antennas-TV-Wifi-and-etc/

alzie alzie6 months ago

PS, the only true wide band fractal antenna is the log periodic dipole array.

jimvandamme alzie6 months ago

I've tested fractals in an anechoic chamber with a network analyzer, and they are wideband, but they can be kind of ratty, with lots of small phase and amplitude perturbations because of the fine grained elements. For small bandwidth signals you can't beat their size, and they match over a wide band. For TV, well, I have a commercial LPDA on my house. You need a nice smooth response over that 6 MHz channel to decode the signal. A bowtie is easy to make though. I've built bowties down to 3 MHz.

Edgar6 months ago

This is neat! So I've voted, and will go all over, because a Link to it is on this Blog of mine:

http://faz-voce-mesmo.blogspot.pt/2014/05/littlebits-farta-e-casas-de-brincar-em.html

jimvandamme6 months ago

There are 2 ways you could substantially improve this project.

First, learn how antennas work. This would help you refine both your design and your testing. You can do a theoretical design based on how much signal is transmitted to your location (e.g., www.tvfool.com), and calculate how much gain you can achieve using antenna books (ARRL handbook is the cheapest) or software. You need to learn about things like matching, directivity, and polarization.

Second, learn how to test them and get useful results. With a converter box, you can read out a relative power measurement on each channel. You can compare this with a standard gain dipole that you build, and get an absolute gain measurement with decent enough accuracy. And you will learn to test in free space, not in an inside room with the antenna against your body.

I'm right there with you on this one. Antennas are much more than they appear to be.
ajanuszczak6 months ago

Very cool! I made the bowtie, which works well but takes up a lot of space. http://www.instructables.com/id/Powerful-Modern-Ho... Your project would fit my available space much better. Well done!

thassaj6 months ago

Very interesting! I used to spend a lot of time designing and building ham radio antennas but I never tried fractal shapes. With the Sierpinsky triangle shape, I would have thought that you would have made two Sierpinsky triangles, with the triangles pointing at each other, but not quite touching. Then the antenna wires would be soldered to the two points that are near each other. It would look like a fractal bow tie. I would guess that such an antenna would behave like a bowtie antenna but would work over a larger bandwidth, especially higher frequencies.

If ham radio were not a dying hobby I would suggest you get your radio licenses and build antennas for long distance (DX) communication - it is great fun to come up with a design that really works well - suddenly you are talking to the other side of the world! Of course today, you can just open a chat box to your friend in China :-)

Have fun, and I hope you young ladies go into science or engineering - we need more female brains in those areas.

repkid6 months ago

I love seeing more Koch snowflakes in the wild. Awesome!

0zzy6 months ago

That is very cool I'll try it one day when I've got some free time thanks

AMasonAHammond (author)  0zzy6 months ago

Thank you! Hope you have as much fun as we did! :)

Ok thanks I'll possibly have ago over the weekend and I'll let you know how I got on thanks again
phonx6 months ago

I've put off the task for a while nice - I'll give a try

akristoffer6 months ago

I've been trying to come up with a good antenna for a bluetooth project I've been messing with, I might try to scale some of your project down and see if I have any success. Unless, of course, you had some plans to to experiment with tiny fractal bluetooth antennae...in which case, you could do the work and I could reap the benefits. Anyway, great instructable. Triangles are my favorite shape!

HoldOnTight6 months ago

I've made fractal antennae and I can say that they work best if you connect your wires between a point on the fractal that you cut. This is why you sometimes achieved better reception with only one antenna wire attached. Try the Koch antenna for example...choose a point on the antenna and cut it then connect one wire to each end. You may have to cut out a very small segment to keep the ends from shorting together, but your reception should be much better! Try it... I'd like to hear how it worked for you. PhilKe2FL also mentions this point.

walshlg6 months ago

well done and well written, I MUST give this a try!

AMasonAHammond (author)  walshlg6 months ago

Thanks! I hope you will let us know how it goes! :)

billbillt6 months ago

This is great... Now we can tell the cable people to "CRAM IT"....

AMasonAHammond (author)  billbillt6 months ago

Glad you enjoyed our Instructable! :)

walshlg6 months ago

well done and well written, I MUST give this a try!

AMasonAHammond (author) 6 months ago

@PhilKE3FL Thank you for providing us with such useful and relevant information! We plan on further testing various types of fractal antennas including an original design of our own. We will most definitely check out your website.

As far as attaching the wires to the antennas, for the aluminum foil fractal we simply maneuvered the wires underneath the foil so they were between the foil and the paper. As far as the Solder Fractal, we used scotch tape to hold the wires in place, and we held the wires against the fractal with our hands, allowing us to experiment with the angle positioning of the fractal. We did the same thing for the Insulated Wire Fractal.

As part of our testing, we did position the wires at different points on the fractals (Solder and Aluminum Fractal), and were met with largely the same results.

In regards to even the amount of wires used, at times the reception was better when only one wire was placed on the fractal at one time instead of two. We believe this may have been the result of self interference on the part of the wires and the fractals.

triforce ftw!

AMasonAHammond (author)  steampunkpotato6 months ago

@steampunkpotato :)

As a child, before the days of cable and satellite dishes, everyone had an antenna on their television sets. When those rabbit ears broke, we sometimes had to be creative until the antenna was replaced. My dad once attached a wire coat hanger to the antenna base which actually worked better than the original antenna. I didn't realize it at the time, but we were using a simple, triangular fractal antenna. Wow, you learn something new every day! Thanks ladies for an excellent instructable.

AMasonAHammond (author)  EatWellLiveWell7 months ago

@EatWellLiveWell Thank you! :)

hossdt277 months ago
As one who has used many junky antenna and successfully building a couple antennas myself, I have been looking for an informative to the point instructable, I am so trying this thank you
AMasonAHammond (author)  hossdt277 months ago

@hossdt27 Glad you enjoyed our Instructable! Happy building! :)

AMasonAHammond (author) 7 months ago

@selias33 Thank you! :)

selias337 months ago
Nice job! Look at all those views and favorites!