LimeSDR Mini Output Power Levels

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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.

LimeSDR Mini Output.jpg

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 13.5
99 12.0 11.6 11.7
98 12.0 11.6 11.7
97 12.0 10.1 11.7
96 10.0 10.1 9.7
95 10.0 9.0 9.7
94 10.0 9.0 9.7
93 6.4 6.8 5.8
92 6.4 6.8 5.8
91 6.4 6.8 5.8
90 6.4 4.8 5.8
89 5.4 4.8 4.8
88 4.4 4.8 3.9
87 4.4 0.5 3.9
86 4.4 0.5 2.8
85 2.4 0.5 1.8
84 1.4 0.5 0.8
83 1.4 -0.5 0.8
82 0.3 -0.5 -0.2
81 -0.6 -1.5 -1.2
80 -1.8 -2.3 -2.2
79 -2.6 -3.3 -3.2
78 -2.6 -4.3 -3.2
77 -3.6 -4.3 -4.2
76 -3.6 -5.3 -4.2
75 -5.6 -6.4 -6.2
74 -5.6 -7.4 -6.2
73 -5.6 -7.4 -6.2
72 -7.6 -8.4 -8.2
71 -7.6 -9.4 -8.2
70 -7.6 -9.4 -8.2