All of the discussion about transmit power seems to be centered around LimeSuite. I wanted to build a transceiver using GNU Radio but could not find information about the correlation between the Tx gain in the gr-limesdr transmit block and the actual output power. I made a simple flowgraph in GNU Radio 3.8 and spent most of the day measuring the output power of the LimeSDR Mini on an Agilent N9000A. Test setup was a LimeSDR Mini into SMA cable into a SMA/UHF adapter hooked directly to a UHF/Type N adapter plugged into the signal analyzer. Measurements span from 30MHz to 950MHz and from a gain of 60 (the maximum allowed value) to 22. I have attached a screenshot of the spreadsheet of measurements (not sure how to upload the actual spreadsheet), as well as images of two graphs characterizing the data. Generally the max output stays between 0.5 and 2 dBm. The gain adjustment is surprisingly linear with respect to output power, with a decrease of 2 gain being roughly equal to a 2dBm decrease across the entire range. The output power also remains relatively constant over the span of measured frequencies.
Hopefully someone finds this helpful.
Worth noting: I didn’t write down the decimal point when recording the data for 30MHz, and ran out of time to go back and redo it.