1/17/2011

TV Antenna and Fractals

There are may plans online on how to make a TV antenna to receive digital signals. But also i just got done watching a NOVA show on PBS about Fractals.

Nova - Hunting the Hidden Dimension

A fractal is an infinitely long line or shape that no matter how much you zoom in, or how detailed you look, the repeating self-similarity pattern is the same.
animated Fractal Gif image, repeating pattern, star fractal, kochsim
For examples of fractals in nature there are things like trees, rivers, clouds, flowers, DNA, blood vessels, snowflakes, lightning and many, many more.
Fractal Fern, repeating leaf pattern, fractal plant, repeating tv antenna http://ontfin.com/Word/wp-content/uploads/2009/06/oxeyedaisy3.jpg,Fractal daisy flower

Here's how fractals are used to create mountains in computer animation in movies. Instead of writing a huge program for each little individual point, the fractal equation is used and it creates the mountain. For example, Jurassic Park used fractals to show raindrops on the dinosaur's skin.
animated gif fractal mountain, http://upload.wikimedia.org/wikipedia/commons/6/6d/Animated_fractal_mountain.gif


This one reminds me of the Triforce in The Legend of Zelda
Fractal triangle pattern, sierpinski triangle

Fractal, triangle, pattern, triforce, zelda

Long story short, it turns out that fractals also make great antennas. They are in all of our cell phones because of their great range of reception and compact size. That's why cell phones don't have those little flimsy pole antennas any more. The fractal antenna is inside.
Fractal, cell phone, antenna

So i started with the basic antenna plans seen here
.
Fractal TV Antenna, make, DIY
Then i took ideas from fractal antennasFractal TV Antenna, pattern, make, build, DIY
I laid everything out that i thought i'd need
Fractal antenna, parts, pattern, wire
This was the basic fractal pattern i used to bend the wire
TV Fractal Antenna Pattern, measurement, dimension, star
The wire after being bent.
Fractal wire, bent, tv antenna
After making 10 of the wire shapes above i started experimenting with them.

3 sided
Fractal wire, bent, tv antenna, parts
4 sided
Fractal, wire,bent, tv antenna, design
5 sided
Fractal, wire,bent, tv antenna, 5 sided, design
6 sided Fractal, wire,bent, tv antenna, 6 sided, design
There were endless possibilities
TV Fractal Antenna star pattern
I decided on combining 3 things:

  • aluminum foil wrapped cardboard backing plate
  • hexagon shaped fractal wire
  • 4 piece wire antenna
Final design for Fractal Antenna to make

This is the upper halfFractal Antenna TV, upper half part
Here it is on the board
. I wrapped the aluminum foil with rubber window screen so that the wires didn't actually touch the aluminum foil. Then secured it with hot glue on top of the solder points.Fractal Antenna TV, foil back plate
1" pvc pipe and bolts were used to raise the upper wires
Fractal Antenna TV, weld, solder, wire Fractal Antenna TV, weld, solder, wire, plate
Here's the finished product
. I connected it to a 75 to 300 Ohm matching transformer, which is really the only thing i had to buy, it was $5. small fractal antenna, tv reception
I also made another version.
small version, fractal tv antenna 75 to 300 Ohm matching transformer, small fractal tv antenna
After connecting them to my tv i was able to check the signal strength. They both worked pretty well, picking up all UHF channels such as 2.1, 4.1, 7.1, .... Although surprisingly, the smaller antenna worked a little bit better. 2 versions of Fractal TV antenna
I plan on trying a few more designs. I think the best idea would be to paint a 7 foot tall fractal design on a wall with metallic paint. It would look cool and possible get great reception. You could always paint over it and no one would know it was there.

7 comments:

Josh said...

You write: " Although surprisingly, the smaller antenna worked a little bit better."... are you talking about the antenna on the left?

Thanks,
Josh

Dave Wirth said...

Ya out of all of the ones i've made the one on the left seemed to work the best.

http://1.bp.blogspot.com/_XJSj8yZNcEM/TT1ztZ8YsYI/AAAAAAAACVI/uvk3zM7vn48/s1600/DSCF1771%2B%2528Custom%2529.JPG

What i really want to do is try something like this. A larger scale, flat wire that would act like a piece of art that you could hang on the wall.

https://lh6.googleusercontent.com/-5iF5m2DfTPI/T0vn1ucgkcI/AAAAAAAAFVM/nFXKJG3Ce3c/s800/2ptnzhk.jpg

Dave Wirth said...

Sorry, here are clickable links:

Small Antenna

Another antenna to try

Josh said...

Thanks for the quick reply.... there is a post on the instructables website dealing with fractal antennas as well. I've built a couple of these and noticed the same results... smaller form-factors work much better... and they have incredible range.... I was able to receive signal in san diego, california from an HD transmitter all the way up in santa barbara (over 150 miles).

Thanks for clarifying.

Dave Wirth said...

There's a ton of different antenna's you can make. It all depends on how detailed you want to get and how much work you want to put into it. Back when i originally posted this i had the idea of using metallic paint and painting a huge fractal pattern on a wall in the house. I still haven't tried that yet and i'm not sure if it would even work.

Also it has a lot to do with where you locate the antenna in your house. High up like in the attic pointing toward the direction of the signal is the best option.

Petrovious606 said...

Hi,

The Foil Backed Antenna will probably work better if you allow about at least quarter wavelength of spacing between the wires and the reflector.

The capacitive reactance absorbs the signal energy when the reflecter is too close to the antenna elements.

A quarter or half wavelength with resonate better with the reflections, say about half to a quarter of the length of the wire before you bend it.

Even better if it is a full wavelength.

Cheers
Peter

Petrovious606 said...

Also is you are making a wall sized antenna I've found their very directional and a Japanese style screen or room divider might be a better option while you are testing it.

I live in the mountains and the best reception I get is from a horizontally orientated antenna. A Ceiling painted antenna might work.

If the floors in your house are ceramic tiled I think the metal minerals in the tiles acts as a ground plane and placing the antenna at the height multiples of the wavelength improves reception a lot.

36.7cm channel is the top of the UHF band and 57cm channel 27 is the bottom of the Australian Channels.

At the moment I am using an indoor Horizontal Double Quad fractal similar to a wifi style cut to channel 34. <>o<>

I get perfect reception on channel 29 32 to 38 with this coat hanger.

I used an old cheap rabbit ears base as the mounting and the steel plate in the bottom also acts a ground plane.

Remember to cut the wires to 95 percent of the signal wavelength because EM travels slower in wire than in the air.

If I can I will post a table of wire lengths.

Cheers
Peter