Both transmitters are equipped with simple wire antennas (82 mm, ¼ wave for 868 MHz). Under particular outdoor urban conditions, we've got transmission distances of more than 200 meters without loosing a single packet!
We should still check these distances under true open field conditions, without near buildings, trees and vehicles surrounding the transmission area. By the moment, results are quite satisfactory, given that these modules have not been designed with the idea of communicating over long distances. Anyway, I feel that we could even improve these distances on future prototypes, just adding bigger ground planes and better tuning the RF filter.
More tests coming soon!