Hello Ian,
It's always advisable to use all antennas for best coverage; however, if you decide not to, then you will have to change the Antenna mode in the config depending on the number of antennas used:
Example, if using 2 antennas on radio 1:
>en
#self
#int radio 1
#antenna-mode ?
1x1 Use only antenna A to receive and transmit
1xALL Transmit on antenna A, receive on all antennas
2x2 Use antenna A and C for both transmit and receive
3x3 Use antenna A, B and C for both transmit and receive
default Use default antenna setting #antenna-mode 2x2 #com wrAssuming the AP is on a recent firmware version.
Regards,
Chris
Christoph S.