LimeSDR Mini Output Power Levels

The output power of the Lime Mini varies significantly across the bandwidth and does not vary linearly with adjustments to the "Lime Gain" on the Portsdown.

Variation with Frequency

The measurements below were made with a LimeSDR Mini using a Portsdown transmitter (version 201812290) at Lime Gain = 88.

The discontinuity at 2 GHz is where the output circuitry is switched between low band and high band.

Variation with Lime Gain

There are 3 modes that respond differently to the Lime Gain parameter: Carrier, DATV with 2x up-sampling and DATV with 4x up-sampling.

For Portsdown software version 201812290, the following Lime Gain settings are most consistent (plus or minus 1 dB) across the modes:

Lime Gain	437 MHz Power
98	11.8 dBm
96	10.0 dBm
92	6.3 dBm
88	4.4 dBm
84	0.8 dBm
82	-0.1 dBm
81	-1.1 dBm
80	-2.1 dBm
79	-3.0 dBm
77	-4.0 dBm
75	-6.0 dBm
72	-8.0 dBm

The use of intermediate Lime Gain values is not recommended as they give inconsistent results. For example at Lime Gain 87, carrier mode generates 4 dB more power than DATV.

For operation at other frequencies, the expected output power should be reduced in line with the graph above.

Source Data

To arrive at the values above, the output power was measured in each mode at 437 MHz:

Lime Gain	Carrier dBm	4x Up-sampling dBm	2x Up-sampling dBm
100	13.5	12.5	Example
99	12.0	11.6	Example
98	12.0	11.6	Example
97	12.0	10.1	Example
96	10.0	10.1	Example
95	10.0	9.0	Example
94	10.0	9.0	Example
93	6.4	6.8	Example
92	6.4	6.8	Example
91	6.4	6.8	Example
90	6.4	4.8	Example
89	5.4	4.8	Example
88	4.4	4.8	Example
87	4.4	0.5	Example
86	4.4	0.5	Example
85	2.4	0.5	Example
84	1.4	0.5	Example
83	1.4	-0.5	Example
82	0.3	-0.5	Example
81	-0.6	-1.5	Example
80	-1.8	-2.3	Example
79	-2.6	-3.3	Example
78	-2.6	-4.3	Example
77	-3.6	-4.3	Example
76	-3.6	-5.3	Example
75	-5.6	-6.4	Example
74	-5.6	-7.4	Example
73	-5.6	-7.4	Example
72	-7.6	-8.4	Example
71	-7.6	-9.4	Example
70	-7.6	-9.4	Example