Still one-way, but it is quite outstanding: my bare HB100 signal could be received by a bare LNB at 32 km distance with a 13 dB S/N margin. I could increase the signal by adjusting the TX direction, but the RX side is fixed on a remote location (remote SDR receiver).
Also I think that the strong wind was waving some vegetation into the path because the signal would disappear with heavy QSB.
What is even more interesting is that the bare LNB is receiving a 3 cm beacon 300 km away! At least now we know a remote site where we could try a super-HB100-DX!