To give credit where due, this project is a rendition of the WiFi Predator, a brainchild of I-Hacked.com. Instead of generalizing and reexplaining every step of this build, I'll provide links to the tutorials and products I used to simply aid the process.
Picking a Router:
The heart of this whole project is the router. You will need one that is compatible with DD-WRT, the open source and awesome firmware I mentioned earlier. Check out the supported devices page to help pick out, or confirm that a router you already have will work.
Installing DD-WRT:
Without installing a modified firmware, the router will perform like normal and simply use the antenna to broadcast its signal very far in the aimed direction. This can be useful, but is not what we are looking for. Use the official installation guide for step by step instructions on installing DD-WRT. Also, pay attention to the notes for your specific router/model in the last column of the supported devices page.
Configuring Wireless Settings:
In order to get the router performing correctly and optimally, read this page on setting up a universal wireless repeater.
Installing AutoAP:
According to the wiki, "AutoAP is a script that continuously scans for open Wi-Fi connections, tests them for validity, and connects to the strongest signal." AutoAP is a great addition to this project because it automates the connection process. It might be bundled into the firmware by default, but if not here are instructions for downloading and installing AutoAP.
Picking an Antenna:
This is where the real fun is. Antennas come in a variety of shapes and sizes. Omnidirectional antennas have 360 degree coverage but significantly less range than directional antennas which have very far range but need to be aimed. For this project, directional is the type of antenna you want. One thing to keep in mind when picking an antenna is its dBi rating. Signal gain is measured in decibels, the higher the rating, the further range your antenna will have. The most common types of directional antennas are Parabolic Dish and Yagi. I purchased my antenna from a company called L-com who make quality parts, really cheap. Look in the 2.4 GHz WiFi Antenna section of their site and pick one that fits your budget/desire.
Connecting the Antenna (Choosing Cable):
By default, most antennas are fitted with an N-Female connector. Most routers have either an RP-SMA or RP-TNC connector on their back, so a conversion will need to be made. Don't make the common mistake of trying to plug an N-Female cable into an N-Female plug! Opposites connect to each other. N-Male to RP-TNC (Female) is and example that would connect an antenna to a router. L-com also makes both cables and connectors so pick the product for your needs.
Mounting:
Aside from making the finished product look totally badass, mounting everything together also makes aiming the antenna fun and easy. Most antennas come with mounting gear and there is no wrong way to go about mounting. I found a cheap camera tripod, drilled a hole through top and bolted the antenna on. Then used the L shaped metal bracket and some Velcro to hold the router on securely.
Additional Info: (Tips)
- Consolidate your shipping price and buy everything from one site or find a local retailer (unlikely).
- Coax cable is very lossy, meaning the signal degrades over length. Look for short low resistance cable for optimal signal strength.
- The higher the gain (dBi) of antenna, the less beam width there is available for aiming. Parabolic dishes with really high gain, 20 dBi and up usually have extremely narrow beam widths. Try aiming a 10 degree wide beam on at point 1000 feet away... Not easy.
- Many routers are literally starved for power when all the modifications are done. If your signal is flaky or non consistent try upgrading to a power supply that can provide a higher current (more amps).
- In an attempt to prevent installing 3rd party firmware, many router manufactures limit their products to the bare minimum amount of RAM and CPU speed required to perform the basic tasks. If you router is randomly rebooting or not behaving like it should, try disabling functions you don't need. For example, AutoAP HTML logging.
I am using...
- Linksys WRT54G Version 6 Router
- DD-WRT Micro with AutoAP built-in
- L-com 2.4 GHz, 14 dBi, Backfire WiFi Dish
- About 4' of N-Male to RP-SMA cable
- RP-SMA to RP-TNC connector
- Vivitar 52" Extending Camera Tripod
- Modified Power Supply, 12 Volts 2 Amps (4x current of the standard AC adapter)
Left Side
Top/Front
Top/Back
I hope this outline is a help to those interested in wireless networking and PLEASE! post your feedback, comments, and questions below! :P
