Quad-Directional Cantenna

[brendanrivers]

Recently I constructed a cantenna for my own wifi, because the antenna on my wifi card broke. So I got to thinking when I noticed how well it worked, why don't I make a few of these, put them somewhere high in the air, and bridge all the connections I can find, for increased bandwidth. (my isp recently capped my bandwidth cause I used too much) So I constructed this:

http://the-better-half.tripod.com/IMG_0007.jpg

http://the-better-half.tripod.com/IMG_0008.jpg

http://the-better-half.tripod.com/IMG_0009.jpg


I have no idea if this is feasible, call me a newb and yell at me if I'm doing something terribly wrong. I understand the construction of these is not really up to par, I barely understand enough about waveguide antennas to have done what I did- My question is this-- Will it work? Can I actually hook this up to my computer, grab some excess RF floating around(so to speak) and bridge it all together? (and do other fun things with people's wifi connections;) )

thanks,

-brendan

[M/Q]

Links do not work.

[brendanrivers]

copy paste them into the address bar

[M/Q]

Hello Brendan,

Interesting to say the least, and I like experimentation as it leads to increased knowledge. So I applaud your effort.

Your next step would be to learn more about the technology and science that you are dealing with. Two very good reference books for 802.11 and Radio Frequency are the following links.

https://www.cwnp.com/store/products/CWNASG.html

http://www.arrl.org/catalog/?category=Antennas,+Transmission+Lines+%26+Propaga tion

You have basically constructed an omni-directional antenna. Some of the problems I see with it are:
1. The small size of the coaxial cable exiting from the actual antenna.
2. That same coaxial cable is of different lengths.
3. The active element inside the can appears to be quite long in the one image, is that the correct length as that is very important?

The first consideration is that you are dealing with microwave frequencies and that forces one to abide by a different set of rules than let us say your normal FM radio frequencies. There are many principals that become important. This link is a good start for the science of microwave propagation and it is done by a fellow amateur radio operator, which makes it more interesting as we like to experiment.

http://www.tapr.org/ve3jf.dcc97.html

I might suggest looking at this antenna design, it is also an omni-directional antenna but it will provide more gain than the setup you have made. Not from the actual antenna aspect, but from the having to connect all four together and that is where a great deal of RF energy will be lost.

http://wireless.gumph.org/articles/homemadeomni.html

One last small sermon. As I mentioned I appreciate experimentation and research as I am one of those types. But, I found it slightly disconcerting when you said you were going to do “fun things with people’s wifi connections”. It is the goal of this forum to help people with wireless needs and interests. I would ask that you please refrain from doing anything to anyone else’s equipment/network. It is not showing the proper respect that we all deserve. Setup your own lab or better yet share the research with a friend who has the same interest.

[brendanrivers]

Thank you, I'll be sure to read all those things, then read what you said again and see if I understand it.

I'm gonna put this thing on my roof sometime in the next couple of days, and then open net stumbler and see whats going on. I'll be sure to report what I find floating 50ft in the air.

[brendanrivers]

and i was just kidding about screwing with other people's wifi connections. the only thing I could really do is look through a bunch of suburbanite home computers. and break them. i stopped doing that in 10th grade. l

-brendan

[brendanrivers]

so i put it on the roof and it didn't pick up anything. and the wire i used for the cantenna in my roof works just as good with the can as it does without the can. what'd i do wrong?

[wiltonh]

You have several problems. The cable you are using is not coax. It appears to be lamp cord. You are dealing with very high frequency here which needs special cable to work correctly. Put canantenna into Google and get a good set of plans. You will need "N" connectors and the appropriate cables.

The second issue is the connecting of several cans in parallel. You need a special splitter to make this work. These are not cheap. I setup some parallel cans and did some signal testing. I did not have the appropriate splitter so I used 50 ohm coax. This is not optimum. Here is a URL:

http://windsurf.mediaforte.com/wifi/wifi_antenna.html

To understand exactly what is going on with your testing, you need to get a copy of Netstumbler and lean to use it. It is a free program which will give eyes to your testing. Testing these things can be a lot of fun.