You can use any 50 ohm 2.4ghz antenna. You must decide on the radiation pattern you need. High gain omni's will give you a 360 degree horizontal pattern but only a few degrees in the vertical plane. (very flat doughnut shape) Directional antennas will give you anywhere from 120 degrees horiz and vert, to a very thin beam of 15 degrees horiz and vertical. (think of a directional antenna as a flashlight with a focusable beam) Keep in mind you need to increase your gain by 6db to double your range. This could be a 3db gain at both ends or 6db at one end. Every 3db more gain doubles your signal strength, but signal strength decreases by the inverse square of the distance. (twice as far away, 1/4 as much signal strength). 0dbd does equal 2.15 dbi. Same as saying a 12dbd antenna is equal to a 14.15 dbi antenna. Think about it.