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Picture of Foil based fractal antenna.
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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.

Picture of 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.
cgosh3 years ago

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.

Computothought (author)  cgosh3 years ago

Thank you for the lecture on radio waves.

cgosh6 years ago
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.
Computothought (author)  cgosh6 years ago
Thanks for the comment.
manuka6 years ago
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/
Computothought (author)  manuka6 years ago
The yagi type antenna is not the only antenna. Does not hurt to experiment a bit. Your needs are different than my intentions.
jsilverman17 years ago
+1 for using tuxpaint
Computothought (author)  jsilverman17 years ago
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.