The same antenna can be and is used for both TX and RX. However, in MIMO, SIMO and MOSI systems, you can have multiple RX antennas for the same TX, multiple TX to RX antennas and basically any number of combinations. Usually in MIMO it's for example 3x3 (3TX and 3RX).

WiFi antenna 1T1R mode
OK, I've waited until I finished ADWD in case there was any explanation there.

Why was Benjen Stark on the Wall? Was there an explanation I have missed?

I appreciate, as a younger brother, he would have had less opportunity than Brandon (or Eddard), and may have been looking for adventure or honour, but the Wall, by the time he would have joined, was hardly at the height of its renown.

Joining the Black wouldn't be, I would have thought, a particularly obvious option for Benjen, if he was simply looking for a title or a role in life to fit the name of Stark.
