A BiQuad is two full wave bisquare antennas in parallel in front of a reflector 1/8 wavelength away. Without the reflector, the propagation pattern is very much like that of a dipole. The reflector drives the beam outward.
What is the gain/beam width? ~ 11dbi with a 50 degree beam
Why should I fly it? There are several advantages to the BiQuad. First and foremost, unlike the patch, this antenna is NOT ground plane dependent. While being close to the ground will actually increase the gain some, it is not necessary. It also has small side lobes in the far field, and thus you can fly in close without flying into a null. There is, however, still a null directly overhead just like a dipole would have.