Introduction: Foil Based Fractal Antenna.

This Instructable is based on a copper based antenna: (https://www.instructables.com/id/How-to-make-a-fractal-antenna-for-HDTV-DTV-plus-/). Took several hours of calculus in college, but was never interested in fractals. After watching a show on PBS about fractals and how many antennas such as cell phones are based of them, I was hooked. I had to try it myself. Did some research and found the instructable this antenna is based off of.  Had already done some other foil antennas. The are cheaper and safer than the hardwired antennas for the most part. Had to try to make a version in foil. This is what I came up with. The antenna is a bit directional, but does ok.

Here are some more antennas you might be itnerested in: https://www.instructables.com/id/Antennas-TV-Wifi-and-etc/

Note: somehow while editing this instructable the text was lost. I have the original somewhare, I will try to find it later.

Original text per www.archive.org/:

If you saw my original (over the air) foil antenna, then you maybe interested in a new antenna I am working on. This is basically a duplicate of Mr. Ruckman's antenna, but it is made with foil instead. Why foil you say? It is easier to conceal in a frame, safer around kids, and I just wanted to try it. For a long time I was not into fractals even with having taken 7 hours of now forgotten Calculus in college. After watching a show about fractals on PBS (Nova?) talking about how most modern cell phones use fractals for antenna shapes, I was hooked. Plan to make a coat hanger version also to see how it compares. Should of added over-the-air antenna to the title. This antenna seems to work best of all the ones I have done so far.

You may also like: https://www.instructables.com/id/Dtv-Antennas-I-have-tried/, https://www.instructables.com/id/Yagi-foil-HDTV-antenna/

Worst case scenario, it makes an interest holiday decoration.

Step 1: What's Needed.

A roll of foil that you can get usually less expensive at the dollar store.
Piece of cardboard to act as a backing.
Tape to put it together. 
Wire
1 coat hanger to make a form.
TV transformer.

Tools
Ruler that can measure in inches
60 degree triangle or equivalent.

Step 2: Make the Form.

Using a form will make it easier to make consistent folds for the antenna sections.
Take a coat hanger and cut an eight inch length out of the bottom part of the hanger. The rest of the coat hanger is unneeded.

Per the original author:

You will repeat this step for each wire. Each bend on the wire will be 60 degrees exactly as we will be making equilateral triangles with this fractal. I used two pairs of pliers and a protractor. Each bend will be made at the 1 marks. Make sure you visualize the direction of each bend first before making it! Use the diagram below to help.

Mine still needs a little tweaking, but you get the idea.

Step 3: Making Each Antenna Leaf.

Unroll 24 inches of aluminium foil. Cut the 24 inches of foil into three 8-inch pieces.
Cut each section so that each 8 inch section is half as wide.
Fold each piece of foil lengthwise in half. Repeat and repeat until you have a foil stick approximately a 1/8 to 1/4 inch wide.
Two of these will be the two long sections. We will use them in a later step

Four or the rest of these will be the fractals.
Take each of the four fractal sections and fold them like your form. This one still needs a bit more work.

 

Step 4: Putting It All Together.

From all the antennas I have tried they all will work to some degree. The better you make onm the better the results will be. Try this one and expect to do some tweaking.

Get an a 8x11 piece of paper or even better cardboard.
Tape down the two main strands so you can add the transformer.
Tape down the transformer.
The add the stars along each of the two strands.

Note: what is pictured is just a prototype, but you get the idea..

Step 5: Alternative Version.

We will take one of those cookie tins and make an alternative verion of the fractal antenna.

Draw two long straight stips in the middle going lengthwise on  the foil.
Use the original form  to draw the fractals. (Just draw around it.
Do this four times till it looks like the fractal antenna.
Cut out the two sections. BE CARFUL THE EDGES ARE SHARP!!
Mount the sections.

Comments

author
cgosh (author)2016-07-18

Unless I miss my guess, this is why this idea works:

Fractals are made up of small pieces that form larger pieces that are multiples of the smallest size.

Radio waves do best with a "resonant" antenna length that resonates to match the radio frequency (which is the inverse of the wavelength -- one goes up, the other goes down). This concept is how a good singer can shatter a wine glass, or how you can fill multiple glasses with a little water to play a chromatic scale. Just match the resonant frequency.

You can also use 1/2, or 1/4, or 1/8, or double or quadruple the resonant wavelength, or other multiples, with proceedingly lesser impact. Think of the difference between Low C, Middle C and High C on a musical instrument -- they're all just multiples of the same resonance.

For example, old Citizens Band [CB] radio antennas were legally limited to a maximum of 20 feet above an existing structure, so they used a 5/8 formula that worked out to just shy of 20 feet. CB car "whip" antennas were 108 inches, which is 9 feet, or 1/4 the 11 meters [36 feet] of wavelength, and 27 mHz in frequency. The actual radio wave is 11 meters, or about 36 feet from top to bottom. Car CB radios use a coil of wire (a loaded coil) in the antenna to make it "electrically" longer. Ham radio operators use multiple coils on a single antenna to make it work well on many frequencies.

Making an antenna that is a multiple (or a simple fraction) of the wavelength -- then making up additional patterns that are also multiples -- strengthens the overall ability for the antenna to transfer the weak radio energy in the air into a usable signal.

With very high frequencies (television, cellphones, wi-fi) the wavelengths -- and thus the antenna lengths -- get very short. Police radio antennas are just a few inches long now, but they used to be 5 feet or 10 feet long when they were on a lower frequency band (55 mHz or around 6 meters -- a double-length 10-foot antenna flopping around allows a bit more distance from the police station, but it's clumsier).

Wi-fi (2.4 gHz, or 2,400 mHz, or 0.125 meters or 125 millimeters) resonant wavelength is 4.92 inches long. But a wi-fi fractal antenna could use lengths of 0.49" (1/8th wave), 0.98" (1/4-wave), 1.96" (1/2-wave), and 4.92" (full-wave) as it's component pieces to achieve a better antenna in a small space. It's like stuffing a bunch of small, resonant antennas inside a big one.

Bottom line? Your TV works on many different channels. Pick the one you want the worst (or get the worst signal) and tailor your fractal lengths to match that wavelength, or make multiple antennas and see if you can leave them all connected. YMMV. Use Google to get the numbers you need ('frequency of channel 3' or 'wavelength of 63 mHz').

A Yagi antenna does the same thing, but with fewer pieces, and it takes the diameter of the tubing pieces into account (yeah, for antennas, everything matters). If you want to learn more, go to your library's Reference section and look at the ARRL Manual.

author
Computothought (author)cgosh2016-08-04

Thank you for the lecture on radio waves.

author
cgosh (author)2013-09-09

For those wondering what the "TV transformer" part is, it's one of those gizmos that used to be used to connect old style 300-ohm twin-lead antenna wire to a 75-ohm coaxial input on the back of a modern TV set. Also called a matching transformer, or a balun (BAY-lun). Should only cost a few dollars.

author
Computothought (author)cgosh2013-09-09

Thanks for the comment.

author
manuka (author)2012-11-03

Good work - but perhaps check a 433 MHz UHF tape measure version which is much more rugged!  See =>https://www.instructables.com/id/433-MHz-tape-measure-antenna-suits-UHF-transmitte/

author
Computothought (author)manuka2012-11-04

The yagi type antenna is not the only antenna. Does not hurt to experiment a bit. Your needs are different than my intentions.

author
jsilverman1 (author)2012-01-14

+1 for using tuxpaint

author

Thanx! Have been using open source for a few years now. We have a another GH type antenna coming out soon, if I can get it finished today.

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