The whole idea here with diversity is not to increase range, but increase transmission quality. With signals bouncing off from everywhere, duplicate packets will reach the antennas at diffrent times. Using diversity, the access point switches between the two antennas, selecting the antenna with the best signal at that given time. Haveing the 2 antennas one wavelength apart will ensure the best possible configuration to catach the signal if it is refracted from multiple paths and multiple copies of packets are sent. Basically the access point can only send packets or recieve packets, not both at same time. Also the access point can only use one of the 2 radios at a time.
