Hubsan specify that the Zino has a range of 1000m.
If you check out the specifications for the Atheros AR1021x used in both the Controller and quad, the receive sensitivity is quoted (at 5.8Ghz/6Mhz rate) as typically -90dBm.
We also know that the power output has been measured at typically 12dBm, and the antenna provide 2.9dBi gain at each end.
Throw all those together, and knowing the free space path loss at 5.8Ghz (107.72dB/Km), we can calculate the typical range.
And guess what we get?
1100m
That's the theory. What would we see in practice?
.
.
That's good enough for me. I can't see me ever needing to go that far.