CC2650 BLE transmitting power constant or non constant?

Hello Mikael,
Yes, the power should be relatively stable. Interference, multi-path propagation (destructive/constructive self-interfering), change in antenna alignment (some types of antennas have considerable difference in gain in different directions) can cause unpredictable change in range and received signal strength. In a large open field without nearby interferes with isotropic antennas (dipole antenna is a close enough alternative) the path loss should be the dominant loss factor.

Thanks for your answer, I can see in some API calls that the TX power can be changed. But it will not be changed automatically???

Perfect thanks! Please let me know what the (other) expert says as well. :)

I tested HCI_EXT_SetRxGainCmd(HCI_EXT_RX_GAIN_HIGH);, This resulted in significally higher noise. I can say that this does not seem to be set dynamically. I also increased the transmit power to 5db, this resulted in much lower noise and a better accuracy = WIN! :)

Hello Mikael,
Nice,
The AGC will impact on the saturation level of the RSSI. The AGC only has two gain levels, so with low gain, the RSSI values reported may be quite a bit higher than with high gain. But as stated before it might have been multi-path propagation effects.