@mfalkvidd
Thanks! That is almost the same as my readings.
@scalz
I have been working few years with ZigBee modules from TI (CC2530). I had dozens of different setups with integrated and also external antenna. RF values was not "just datasheet numbers", if there was written 20dBm output, it was there.
But fully agree, that here is the problem mainly caused by non-optimized antenna... So there is a huge space to increase the range of modules...
And one more update, whch I think can be very important for all others. My setup is running on OpenHab2 installed on OrangePi Zero with SerialGateway connected over UART.
Just now I had realised, that OrangePi makes huge RF noise. If I will run setup normally, receiving sensitivity is very poor. Once I start setup without SD card inside of the system (OrangePi will not start up), Arduino gateway is receiving perfectly.
I have just putted SerialGateway to the 50cm long cables, far from OrangePi and usable range is more than twice longer than before.
Thans for your time guys. Appreciated.