LimeSDR power levels

I did some measuring of power levels off my LimeSDR Mini.

Setup:

• GRC 3.8 on Linux
• Signal source block - 800Hz sine wave
• LimeSDR sink block - 144MHz
• LimeSDR mini -> eBay "1MHz to 6GHz 70dB Logarithmic Detector"
• 30dB attenuator as required

Data: https://docs.google.com/spreadsheets/d/1yNWBUtQVUclWzVoxHM_TIjFW0IjceRJycnshdcvirWg/edit?usp=sharing

The table below shows measured power output for each of the distinct gain levels the driver will accept. Each data point is taken from the more linear of the two series in that part of the source data, or the approximate mean in the centre portion. (One series was measured with a 30dB attenuator, the other without, to capture a larger range.)

LimeSDR driver power level	Measured dBm output
14	-44.8
16	-42.4
18	-40.1
20	-38.1
22	-36.1
24	-34.1
26	-32.0
28	-29.9
30	-27.9
32	-25.8
34	-23.7
36	-21.5
38	-19.5
40	-17.3
42	-15.5
44	-13.4
46	-11.4
48	-9.4
50	-7.1
52	-5.1
54	-3.1
55	-2.4
56	-1.4
57	-0.3
58	0.6
59	1.7
60	2.8
61	3.8
62	4.9
63	5.8
64	6.9
68	11.0
70	13.1
72	15.2
74	16.2

The linear portion of the data (i.e. gain settings 14 to 72 inclusive) is:

Output in dBm = 1.0344827586207 x gain setting – 59.28275862069

or approximately:

Output in dBm = LimeSDR gain setting - 60