Today I run a test with my DIY 868MHz Yagi antenna.
Two Wi.232 modules were used to create a datalink. The transmitter module was sending GPS NMEA strings at 9600Baud while the receiver module was mounted on my antenna tracker, where the data was shown.
The modules were set to 15dBm output power. A 1/4 Lambda whip antenna was used on the transmitter while the Yagi was on the receiver.
When I reached a distance of 10km with direct line of sight to the transmitter I stopped the test. Data reception was stable at this point and the Yagi is proofed to work perfectly.