I just found that the secondary antenna for wifi on vocore2 is disabled by default. So this is SISO with onboard antenna by default. The link below gives commands to bring the second antenna up to get MIMO working which might require at least 6cm spacing between the two antennas to prevent cross talks.
Is there any command to disable the power of the onboard antenna? I'd like to use the secondary antenna only while turning off the onboard antenna. This way I could hook up with high gained antenna connected to U.FL to get better coverage.
http://vocore.io/v2.html
enable second antenna:
/tmp/factory 0x34 0x22 > /tmp/mtd2.tmp
mtd -e factory write /tmp/mtd2.tmp factory
disable second antenna:
/tmp/factory 0x34 0x11 > /tmp/mtd2.tmp
mtd -e factory write /tmp/mtd2.tmp factory