# Make a Fractal Antenna for HD + Digital TV (2 of 4)

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By: psb2usa

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Video Discription: More fun with Fractals......
Fractal Antenna
From Wikipedia, the free encyclopedia
"An example of a fractal antenna: a space-filling curve called a Minkowski Island (ref 1).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.
Such fractal antennas are also referred to as multilevel, and space filling curves, but the key aspect lies in their repetition of a motif over two or more scale sizes,[1] or 'iterations'. For this reason, fractal antennas are very compact, are multiband or wideband, and have useful applications in cellular telephone and microwave communications.
A good example of a fractal antenna as a spacefilling curve is in the form of a shrunken fractal helix [2] Here, each line of copper is just small fraction of a wavelength.
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 used—and thus the standard antennas only work well at that frequency. This makes the fractal antenna an excellent design for wideband and multiband applications....
Fractal element antennas and superior performance
Antenna elements (as opposed to antenna arrays) made from self-similar shapes were first done by Nathan Cohen,[3] then a professor at Boston University, starting in 1988.
Cohen's efforts with a variety of fractal antenna designs were first published in 1995 (thus the first scientific publication on fractal antennas), and a number of patents have been issued from the 1995 filing priority of invention (see list in references, for example). Most allusions to fractal antennas make reference to these 'fractal element antennas'.
Many fractal element antennas use the fractal structure as a virtual combination of capacitors and inductors. This makes the antenna so that it has many different resonances which can be chosen and adjusted by choosing the proper fractal design.
Electrical resonances may not be directly related to a particular scale size of the fractal antenna structure. The physical size of the antenna is unrelated to its resonant or broadband performance. The general rule of antenna length being near target frequency wavelength does not apply itself in the same way with fractal antennas.
This complexity arises because the current on the structure has a complex arrangement caused by the inductance and self capacitance. In general, although their effective electrical length is longer, the fractal element antennas are themselves physically smaller.
Fractal element antennas are shrunken compared to conventional designs, and do not need additional components. In general the fractal dimension of a fractal antenna is a poor predictor of its performance and application.
Not all fractal antennas work well for a given application or set of applications. Computer search methods and antennas simulations are commonly used to identify which fractal antenna designs best meet the need of the application.
Although the first validation of the technology was published as early as 1995 (see ref.1) recent independent studies continue to show the superiority of the fractal element technology in real-life applications, such as RFID....."
http://en.wikipedia.org/wiki/Fractal_...
This video is of my first build of a FRACTAL ANTENNA as seen on...
http://www.instructables.com/id/How_t...
full instuctions and dimentions can be found there.
Results were AMAZING. I would say this antenna is around 90% as efficient as the regular "Coat Hanger" type antennas I have been building recently. Do not be put off by the size of this antenna as it really does perform well. Adding a reflector seemed to help slightly, but I had to space it around an inch from the antenn for best result. When mounted in the Blue satellite dish it works best of all but became very directional (What you want) I will be adding more videos and results shortly here and on VisionPlus.US
More DIY projects like this on the VisionPlus.US Forum
www.VisionPlus.US