There are 2 radios in the DIR-655 (1 for 2.4 GHz and 1 for 5GHz). However the 5GHz radio only uses one antenna and is only accessible on either an 802.11a or 802.11n wireless adapter and has more limited range. The other 2 antennas are for the 2.4GHz, this is to give you better coverage area for 802.11g and 802.11n. The later model was able to incorporate newer technologies to allow an antenna to use both 5GHz and 2.4GHz on one antenna without degradation of signal.