The two antennas on the main and auxiliary SMA ports will work together to increase data throughput. In addition, the auxiliary antenna also acts as a backup to the main antenna.
Do I need to connect an antenna to the auxiliary SMA connector to connect to a LTE service?
We always recommend connecting both antennas to the SMA ports for better throughput. However, if that is not possible, a single antenna on the Cellular Main SMA connector is enough to connect to a LTE service.
Note: The main antenna is used for transmit, and both Main and Aux antennas are used for receive.