What 1T1R and 2T2R mean
T is transmit, R is receive, and the number is how many radio chains there are. 1T1R has one chain and needs one antenna connector on the carrier. 2T2R has two chains and needs two antennas, using MIMO to send and receive two signals at once. The antenna count is a hardware property of the Wi-Fi chip and cannot be changed in firmware.
Why dual antennas reach further
Two antennas pick up two copies of the same signal over different paths, and the receiver combines them, which helps when the signal is weak or full of reflections. The long-range Wi-Fi module also has higher output power and receive sensitivity. Together these give more range and better penetration than a single antenna, at the cost of a second antenna, more mechanical work and more cost.
Plan antenna positions on the carrier
The point most often missed: if you choose a 2T2R module, the carrier and enclosure must have room and routing for two antennas. A carrier drawn for one antenna and later moved to two means a new board and new tooling. If the distance is uncertain early on, reserve two antenna positions from the start.
AIC8800-D40 (30 – 100 m) and AIC8800-D80 (100 – 300 m) are single-antenna 1T1R. RTL8812CU (300 – 1000 m) is dual-antenna 2T2R, so the carrier needs two antenna positions. The spec sheet also notes 4T4R as a custom option. The ATE946X-KIT uses external SMA antennas and can be ordered with any of the three Wi-Fi modules.