J5 on ar750

Inside the AR750 there are three antenna connectors. One has antenna attached. One is below it less than 2cm. J5? J15? What does this do?

Also there is a third on the bottom. What does this do? (I am drilling holes to attach external antennas.) Thank you.

The one with antenna attached may be 5G wifi.

The other two connector is for radio calibration. You cannot connect external antennas.

You can check here GL-AR750 (Creta) - GL.iNet Docs