Im trying to find a powerful directional antenna to pickup a signal about 500 feet from one concrete building to another. I tried using a 7dB omni, but it wasnt anywhere near powerful enough to pickup the signal.

All I could find was a 12dB Cantenna, and a 14dB Yagi Cantenna, anyone perhaps know if there would be any real significant gain between the two cantennas?

After that all I could find were 18db+ dishes which I would like to avoid using if at all possible.