Can the MIMO enabled radio of the 50-series be used in SISO mode?

The 50-series radio is a MIMO ? Multiple In / Multiple Out, meaning it is using two parallel paths for WiFi communication in order to increase data throughput, range and link robustness. The driver and the firmware for the 50-series expects two antennas to be present. Hence using the 50-sereis in SISO mode is neither supported nor recommended.