lately I have been gathering a bit of fun toys for “penetration testing” one of the more impressive pieces I recently picked up was a wifi yagi antenna I picked up for under $10!
While expectations weren’t very high for this antenna with it coming from Ebay, and being under $10, after getting it I am truly surprised at the quality of the antenna. It is well tuned to 2.4ghz and is actually 25dBi gain as advertised (tested on an Agilent E8364c network analyzer) and after bolting on a cheap table top camera tripod I now have a very nice little piece of gear.
There is a public hotspot near my house that I was previously barely able to connect to and I could just barely pull up my email using my laptops stock antennas. After hooking this antenna up to my new Alfa AWUS036NHR 2,000mW USB network adapter I now have a perfect signal and can stream Youtube ad Netflix without issue. The only issue that one may have with an antenna like this is that it is a directional antenna that requires you to point the antenna in the direction of the access point you are trying to connect with. It is not difficult to do though because there are plenty of programs available that test signal strength. Without ever knowing where This public access point is located I was able to point my antenna in its direction by connecting to the hotspot and spinning the antenna slowly until I found what direction had the best signal strength.
This is also a really great tool for finding what networks are in your area because With a high gain antenna I can now pick up about 3 times as many networks than I could previously.
By using a directional antenna instead of the stock Dipole antenna that the network adapter comes with I am able to take advantage of a little known exception the the FCC’s rules that allows for a 60 watt wifi link. check out this episode of Hak5 for more information.
There is also a really great EIRP calculator here: http://www.csgnetwork.com/antennaecalc.html
This calculator will allow you to run all the numbers on your own system should you choose to do a bit of playing with higher powered wifi links.