I recently purchased a Hawking Antenna. It was really cheap because it rattled. That was because the antenna mount was slightly broken and it was easily fixed with some glue.
Anyway the antenna is actually an ordinary antenna with a metal reflector. I will give the measurements shortly. Basically you can easily make it yourself. If you carefully pull the top end off you can then see how it works. Hopefully I will be able to do some comparison tests too.
The metal shield/Reflector is about 1.25 inches from the center of the antenna. In my tests this antenna combined with an EDUP USB wireless card detected twice as many wireless networks in our area compared to the built in wireless adapter in my notebook computer.