Do not use a "T connection" to get one AP to service two antennas: This causes many problems, further described below. By "T connection," we mean T-adapter to combine two antennas onto the same antenna cable.
A "T" is the incorrect way to split to antennas or transmitters. It results in a 2:1 impedance mismatch. That in turn, will cause signal degradation and probably equipment failure. You must use a "power divider" or "antenna combiner" device to operate two antennas from one transmitter. These devices are not expensive, and they are necessary. There are many variations on the concept, but the end result is that a 50 ohm load is presented to the transmitter, and each antenna "sees" a 50 ohm transmitter as well.
Posted by George Hardesty on 26th Apr 2019