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How to make a fractal antenna for HDTV / DTV plus more on the cheap

Author: William Ruckman / On: Wednesday 31 December 2008 - 19:26:43
Version 1, Updated 12-31-08.

Here is a link to the part of the Nova episode that inspired this design (Hunting the hidden dimension):

http://www.pbs.org/wgbh/nova/programs/ht/tm/3514.html?site=34&pl=wmp&rate=hi&ch=3

The first thing I would like to discuss is a little history, theory, and uses for fractal antennas.

Fractal antennas are a recent discovery. First discovered back in 1988 by Nathan Cohen and later published and patented in 1995. A fractal antenna has a few unique attributes as seen in this definition from Wikipedia:

"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."

What exactly does that mean? Well, you need to know what a fractal is. Also from Wikipedia:

"A fractal is generally a rough or fragmented geometric shape that can be split into parts, each of which is (at least approximately) a reduced-size copy of the whole,a property called self-similarity."

So basically, a fractal is a geometric shape that repeats and appears over and over no matter how far out or how far in you zoom magnification. For visual clarification, here is a picture of the patented antenna:

Source: Wikipedia and http://patimg2.uspto.gov/.piw?PageNum=6&docid=US007088965 Patent number: 7088965]

Fractal antennas have been found to be approximately 20% more efficient than normal antennas. Which could be useful. Especially if you want to make your own TV antenna to pick up over the air digital or high definition video, increase your cellular range, wifi range, FM or AM radio reception, and so on. Most cell phones already have built in fractal antennas. If you noticed in the past few years that cell phones no longer have antennas on the outside. That is because they have a internal fractal antenna etched on a circuit board which allows them to get better reception and pick up more frequencies such as bluetooth, cellular, and WIFI all from one antenna at the same time!

Wikipedia info:

"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."

The trick is to design your fractal antenna to resonate at what ever center frequency you wish to receive. Which means it will look different and be sized different depending on what you want to receive. A little math can be used to figure this out. (Or a online calculator)

In my example, I am going to make a simple one but you may want to make a more elaborate one. The more elaborate the better. I will use a spool of 18 Gauge solid core wire to make a antenna as an example but you could go as far as to etch your own circuit boards for aesthetic reasons, to make it smaller, or more elaborate with more resolution and resonance.

I am going to use the example of making a TV antenna for digital or high definition reception for over the air broadcasts. It is easier to work with these frequencies and they fall around half a foot to a few feet in length for half wavelengths of the signal. I am also going to base it off a common dipole antenna for simplicity and cheapness of parts for VHF. For UHF you may want to add a director or reflector which will also make it more direction dependent. VHF is direction dependent as well but instead of pointing directly at the TV station like UHF you want VHF rabbit ears (dipole antenna) to be perpendicular to the TV station. But there is a little more design to that. I want to keep this as simple as possible as it is already a very complex subject.

To start, you may want to find what frequencies you want to receive or broadcast.

For TV, here is a link to a frequency chart:

http://www.csgnetwork.com/tvfreqtable.html

This is a great site to help choose a antenna, find channel direction on a compass, antenna type (directional/omnidirectional), channel numbers for digital and analog, and so on. Check it out:

http://antennaweb.org or http://tvfool.com/

And to calculate the size of the antenna we will use a online calculator like this one:

http://www.kwarc.org/ant-calc.html

Here is a good PDF on the design and theory:

http://www.phd.etfbl.net/files/Works_PDF/Poprzen%20Nemanja%20.pdf

How to find the wavelength of a signal:

Wavelength in feet = (coefficient of the speed of light in feet) / (frequency in hertz)

Coefficient of the speed on light in feet = 983571056.43045
Coefficient of the speed on light in meters = 299792458
Coefficient of the speed on light in inches = 11802852700

EXAMPLE HOW TO START: (VHF/UHF dipole array with reflector which works well for a wide range of frequencies DB2):

(350Mhz - 8 inch quarter wave - 16 inch half wave - which falls in the Super Band - between channel 13 and 14 which is a center frequency between the VHF and UHF band for best resonance)
This can be adjusted to work better in your area as your channel spread may be lower or higher on the band.

Based on ( http://uhfhdtvantenna.blogspot.com/ and http://budgetiq.wordpress.com/2008/07/29/diy-hd-antenna/ and http://members.shaw.ca/hdtvantenna/ and http://current.org/ptv/ptv0821make.pdf ), only the fractal designs allow it to be more compact and responsive and we will be using the DB2 model which has high gain and already is pretty compact and popular for indoor and outdoor installs.

Basic supplies (cost me about $15):

Mounting surface such as the plastic project enclosure (8"x6"x3"). http://www.radioshack.com/product/index.jsp?productId=2062285
6 screws. I used steel self tapping sheet metal screws.
A impedance matching transformer 300 ohm to 75 ohm. http://www.radioshack.com/product/index.jsp?productId=2062049
Some 18 gauge solid hook up wire. http://www.radioshack.com/product/index.jsp?productId=2036274
RG-6 coaxial with terminators (and rubber jacket if mounting outside).
Aluminum if using a reflector. The enclosure above came with one.
A sharpie marker or equivalent preferably with a fine tip.
Two pairs of small needle nose pliers.
A ruler of at least 8 inches.
A protractor to measure angle.
A drill and drill bit that is smaller diameter than your screws.
Small wire cutter.
Screw driver or screw gun.

NOTE: Someone was nice enough to create this paper template and post it to http://instructables.com in the comment section. If you prefer to use the paper template I have made it available HERE
HDTV / DTV construction PDF paper template

Step one:

Assemble the enclosure with the reflector under the plastic cover.

Step two:

Drill small tap holes on the opposite side from the reflector in the following positions and place a conductive screw.

Step three:

Cut four 8" pieces of the solid core wire and strip it bare.

Step four:

Use a marker and mark every 1" on the wire. (This is where we are going to make the bends)

Step five:

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.

Step six:

Cut 2 more pieces of wire at least 6 inches long and strip them. Bend these wires around the top and bottom screws going longways and contact the center screws. So all three are contacted. Use the wire cutter and trim unneeded wire.

Step seven:

Place and screw down each of your fractals to the corner screws.

Step eight:

Attach the impedance matching transformer across the two center screws and tighten them down.

COMPLETE!

NOTE: The bottom of the antenna is to the right of this picture where the transformer sticks out.

You may now test your build!. Hook it up and try it out! It worked great for me!

As you can see from the pic below, each time you divide each section and create a new triangle the length of the wire is the same but can fit in a smaller space by taking up room in another direction.


Note: I am not an expert on the subject and I don't assume to have all the answers or information 100% correct. So please, if you find any mistakes feel free to contact me and let me know and I will correct it.



Windows updates not installing?
Author: William Ruckman / On: Thursday 11 September 2008 - 13:01:30

I recently had an issue with a new computer where it refused to install any new updates. Turns out that it was a .dll issue. This was done on a Windows XP SP3 machine so I am not sure if it will work on Vista. But this batch file will fix Windows XP update issues in a snap!

@echo off
net stop WuAuServ
del /Q /S %windir%\SoftwareDistribution
regsvr32.exe %windir%\system32\wuweb.dll
regsvr32.exe %windir%\system32\wups2.dll
regsvr32.exe %windir%\system32\wups.dll
regsvr32.exe %windir%\system32\wucltui.dll
regsvr32.exe %windir%\system32\wuaueng1.dll
regsvr32.exe %windir%\system32\wuaueng.dll
regsvr32.exe %windir%\system32\wuapi.dll
net start WuAuServ

Oh, and…YOUR WELCOME!



LAMPP / XAMPP start up script for CentOS / Fedora / Red Hat
Author: William Ruckman / On: Tuesday 22 April 2008 - 14:09:31

Here is a little script that may help you out if you want to start LAMPP as a service on linux using chkconfig and service commands.

Place the following code in “/etc/init.d/” with the file name “lampp” and make sure it is executable.

#!/bin/sh
#
# author: william ruckman ruckman.net
#
# chkconfig: 2345 98 83
#
# description: Starts and stops the LAMPP Server
#
# processname: lampp

# Source function library
. /etc/rc.d/init.d/functions

# Source networking configuration.
. /etc/sysconfig/network

# Check that networking is up.
[ $ = “no” ] && exit 0

RETVAL=0
# See how we were called.
case “$1? in
start)
echo -n “Starting lampp service: ”
echo ” ”
cd /opt/lampp/
./lampp start
sleep 1
RETVAL=$?
;;
stop)
echo -n “Stopping lampp service: ”
echo ” ”
cd /opt/lampp/
./lampp stop
sleep 1
RETVAL=$?
;;
restart|reload)
echo -n “Restarting lampp service: ”
echo ” ”
cd /opt/lampp/
./lampp restart
sleep 1
RETVAL=$?
;;
status)
echo -n “Checking lampp service: ”
echo ” ”
cd /opt/lampp/
./lampp status
sleep 1
RETVAL=$?
;;
*)
echo “Usage: lampp ”
echo ” ”
exit 1
esac

exit $RETVAL

Happy coding!



EeePC Xandros Added Repositories
Author: William Ruckman / On: Friday 17 August 2007 - 20:56:00

Add the following lines to your /etc/apt/sources.list

deb http://xnv4.xandros.com/xs2.0/upkg-srv2 etch main contrib non-free
deb http://dccamirror.xandros.com/dccri/ dccri-3.0 main
deb http://www.geekconnection.org xandros4 main

To protect your default install, you must activate pinning so that your main distribution packages don’t get overwritten. Which could possibly cause stability issues.

Add following lines to /etc/apt/preferences (if it does not exist, create it).

Package: *
Pin: origin update.eeepc.asus.com
Pin-Priority: 950

Package: *
Pin: origin xnv4.xandros.com
Pin-Priority: 900

Package: *
Pin: origin dccamirror.xandros.com
Pin-Priority: 850

Package: *
Pin: origin www.geekconnection.org
Pin-Priority: 800

You can then use apt-get to install additional software.

ADDITIONAL REPOSITORIES:

Video Lan (VLC) testing repository:
deb http://download.videolan.org/pub/videolan/debian/ sid main

Video Lan (VLC) testing source repository (For downloading source):
deb-src http://download.videolan.org/pub/videolan/debian/ sid main

Tor Debian Repository:
deb http://mirror.noreply.org/pub/tor/ sarge main

Tor Debian Repository (For downloading source):
deb-src http://mirror.noreply.org/pub/tor/ sarge main

More Debian Multimedia mirrors can be located here:

http://www.debian-multimedia.org/mirrors.html



Fix slow login on Windows when offsite from domain
Author: William Ruckman / On: Wednesday 20 June 2007 - 21:06:00


I recently ran into a interesting issue where a Windows Vista machine would wait for 2 minutes to login after the password was typed in. But it would only occur when the laptop was connected to a network with internet access that was not its normal domain network.

After hooking the laptop to a hub with another PC, i started Wireshark to log all packets. After sifting through the data I found that it was attempting to connect to the primary domain controller by domain name, and consecutively trying to connect to all 5 secondary domain controllers by domain name.

What I found was that the domain names were not pointing to the domain servers across the internet, which would be dumb, but were trying to resolve the domain using yahoo name servers which didn’t know the internal sub domains. It was connecting to Yahoo’s name servers because that is who they have hosting their external DNS for them. Yahoo’s name servers redirected the connections to their main website instead because it was a catch-all address.

The problem is in three different places here.

1. Split DNS is being used - They are using a internal DNS server to resolve their subdomains internally, but these subdomains are not known externally so when they are remote they do not resolve properly.
2. A catch-all address is being used on yahoo’s name servers - This is causing any unknown subdomains to be redirected to the main domain name. Which in this case, is the main website which doesn’t house the domain server.
3. The requests are hitting yahoo’s firewall and it is dropping the packets instead of sending a ICMP error message - This is causing the TCP connections to hang for the default amount of time causing windows to wait before logging in.

This problem is obviously caused by DNS issues. In order to remedy the problem, I had to fix the broken split DNS issues.

To do this you have two options:

1. Remove the wildcard from DNS.
2. Redirect the problem subdomains to 127.0.0.1

Removing the wildcard from DNS is the preferred solution. This will cause the DNS server to report “no such name” which will terminate the connection before it is established.

If you cannot remove the wildcard from DNS then you will want to manually make DNS records that point to 127.0.0.1

Such as:

* subdomain1.example.com > 127.0.0.1
* subdomain2.example.com > 127.0.0.1

This will cause the connection to redirect to your localhost when offsite using global DNS. Your localhost will then report that connection unusable which will terminate the connection right away.

The boot up times decreased by 75%!

From 2 minutes to 30 seconds. That is an improvement! The lesson here is to make sure your DNS is correct.

Although, it would be nice if Microsoft would release a patch that would do this in the background after it loads your desktop instead of waiting for the connections to terminate!

I would also like to thank the genius who set up the DNS incorrectly and created all this wonderful work for me. Much appreciated!
Ruckman.net owned and operated by William Ruckman

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