I would like to know what the default value is for the radio TX power for the nRF5240. According to Nordic's specification, the output power is programmable from +8 dBm to -20 dBm. I see there is a CLI command added txpowermax in the OpenThread stack repository, but I believe the latest version is not yet updated on the SDK for Thread.
I also checked the diag power command and see the TX power is given a default value of 0 dBm. Is this just the radio TX power for diagnostics purposes?
The default output power is 0dBm (1mW).
You can change the output power by using the otLinkSetMaxTransmitPower(..) function in the openthread libraries.
I don't know how I missed that function in the API, thanks for that.
Would it be advisable to change the TX output power to a higher value other than 0 dBm?
That depends on your use case. The drawback of increasing the output power is that the average current consumption increases, so if battery life is very important you might want to take that into account.
I would suggest you do some testing at 0dBm and see if you get the range you need, and if you feel it is not sufficient then you can increase it to +4 or +8 dBm.
For reference each 6dB increase of the output power should double the range.
Battery consumption is somewhat important for now. As you suggested, I will keep the output power at 0 dBm till I can run some tests to determine the power consumption of each node. I have multiple routers which will also help in the extending the range. I'll keep an eye on the RSSI and LQI when I test the rest of the network.