The plus and minus has nothing to do with the TX and RX either, as pix told you it is +45 and -45, that means the – port the antenna you are is a cross polarization. Polarization is divided into horizantel, vertical and cross. Cross polarization antennas are much difficult and much expensive than Horizantel and vertical. It is the way it sends the signal, is it up and down(vertical) is it left and right(horizental). Cross polarization has a better sending and receiving of signal and is less vunerable to climate changes. If you see and antenna with one port it is either vertical or horizantel.
Abdel