There's another thread on this:

https://groups.google.com/forum/m/#!searchin/rec.aviation.soaring/Multiple$20GPS$20antennas/rec.aviation.soaring/ovwxmlKN3Iw

This can help with the quality of reception, admittedly at a mild chance of loss of redundancy should the antenna self destruct mid flight. I can't recall ever hearing of such a case.

My intent is to share an antenna amongst FLARM and 2 Clearnav boxes using the divider described in that post and run the TN72 off a separate antenna located further back in the glider, away from the shared one to minimize RF interference.