Long Distance Wifi Project

To communicate with wifi devices there are two methods. Adhock mood or using an Access point. Since access points are not so powerful, it can’t communicate with devices which are away from access point (about 100m). To communicate with far away devices we need to have good antennas other than default 2 dB antennas. I’m also doing the same thing here and I used a U.S. Robotics 802.11 G access point because it’s power full than Linksys. I designed few antennas and fixed to the access point and to my laptop to extend the connectivity.

· Types of Antennas
There are various types of antennas we can use for wifi range .

Waveguide antennas Yagi antennas Parabolic antennas Cantenna

· Antenna Selection
Waveguide antennas are good when we are communicating with large area. Normally waveguide antennas can cover up to 90o to 120 o ( It depend’s on the design of your antenna). You can get an output between 15dB-17dB using waveguide antenna. (for more information about waveguide antennas refer to - http://www.trevormarshall.com/waveguides.htm ). Yagi antennas good for point-topoint communication and it’s also having an output power of about 15dB. This is suitable when you are connecting two locations . Most of the time Cantennas use to increase signal rate if user getting low signals with connectivity. Usually Cantennas use for client side ( for Laptop or workstation).

If we are having 3 or 4 Waveguide antennas, we can cover an area of 360o (same as a GSM tower). But I tried Yagi antenna other than Waveguide antenna because both are having same output power. Because of that working distance also should be the same. I used a Yagi antenna for Access point. I used a regiform as antenna bar and use one meter length of 14 AWG solid copper wire.

I used a Cantenna for my laptop. Because we are using 2.4GHz for 802.11b/g , the diameter of the “Can” should be 3.25”(inches). Minimum length should be 7.46”(inches) (for more information http://www.turnpoint.net/wireless/cantennahowto.html ).

I found a “Can” with exact diameter so it works fine.

· Testing
I fixed a wifi card to my laptop and connected it with the cantenna. Normally wifi cards for laptops are much expensive. Because of that I got a wifi PCI card for desktop computers which is having a mini PCI card internally and plug it in to the laptop.



I connected my access point with the Yagi antenna and placed on a top of a tree.

When we are designing an antenna, measurements should be correct to the last decimal point because we are dealing with micro-wave signals. (for more information http://www.ab9il.net/wlan-projects/wifi6.html ).

When we are testing cantenna we could connect up to 200 meters long, Because of that we created another yagi antenna and use yagi antennas for both Access Point and Laptop.

After that we could communicate up to 300 meters with good data transfer rate.

Defects

1. We didn’t have an open space which is about 1km to test the vvantennas and the connectivity.
2. Our signals were covered by a tree.

But according to results which we got, we can guess that this will work about 1km.

(For more information , gayan@negomp3.com)