Range with 0 dBm and +4 dBm

[Julian]

Hello,

i have a question about the range. I have a Bluetooth-Module with nRF52832. I tested it in my Office. Additional I can Change the Output power from +4 dBm to 0 dBm. On my Smartphone I installed the nrfConnect app for connecting with the module. I tested the range of the different Output powers. When I set the Output power to -40 dBm the range was very slight. Then I determined the range for 0 dBm and +4 dBm. There are several walls wich are made of foam and other items between the Bluetooh-Module and my Smartphone. But I can't recognize a difference between the range with Output power 0 dBm and +4 dBm. Why isn't there a difference? I thought the range would be higher when the Output power is increased.

Thank You for your answers

[endnode]

Well simply your conditions are not set for seeing such small differences. All these objects and reflections in typical indoors environment are causing up to +-20dBm effects in signal strength so any smaller difference at the transmitter can be lost in these fluctuations.

[Julian]

Thank You for the answer. If I test the range outside on a large field I could recognize a difference between 0 dBm and +4 dBm?

[endnode]

Yes, if you e.g. place two same DevKits with the same on the same place, turn Tx Power on one to 0dBm and +4dBm on the other you should notice difference in signal strength on free-air. However it's very hard to do these tests accurately for 2.4GHz radio without proper (expensive) laboratory equipment like isolated chamber etc. because even ground and other objects will influence signal strength. You can do simple experiment: open Nordic nRF Connect app with RSSI graph view on your phone and try to observe how phone's receiver "sees" some beacons around you. You should notice that even if you are staying and the beacon is static as well the signal strength isn't flat but oscillates in the range of at least few dBm (but typically +-5-10dBm). This means that even small changes in the environment (someone goes around, something happens in another room 10 meters from you) are problem.