An Amateur Radio friend of mine (who is very experienced in analogue video and RF, but a newbie to SDR) purchased a LimeSDR Mini from Mouser in August, and has used it successfully for Digital Amateur Television transmissions on 437 MHz. However, when he came to use it for satellite transmissions on 2409 MHz, he found that the output was much lower than expected (although the spectrum is as expected). He has passed it to me to compare with other LimeSDR Minis and ask for an RMA.
Using the Portsdown DATV transmitter, the output on various frequencies is as follows:
146 MHz 437 MHz 1255 MHz 2409 MHz 3000 MHz
+3.0 dBm +4.5 dBm +4.2 dBm -12.4 dBm -17.2 dBm
A known good LimeSDR Mini, connected to the same hardware and test rig gives:
+5.9 dBm +5.7 dBm +5.8 dBm -2.0 dBm -12.5 dBm
It appears to me that the high band output circuitry has a fault, and if I (incorrectly) select the high band output at 1255 MHz, the output is still 10 dB lower than a good LimeSDR Mini with the same settings.
It also fails LimeQuickTest (using the latest LimeSuite, with nothing connected to the SMA sockets, and straight from cold):
pi@raspberrypi:~ $ LimeUtil --update
Connected to [LimeSDR Mini [USB 3.0] 1D587F46DB6271]
Existing gateware is same as update (1.30)Programming update complete!
pi@raspberrypi:~ $ LimeUtil --make
Make device
Device name: LimeSDR-Mini
Expansion name: UNSUPPORTED
Firmware version: 6
Hardware version: 3
Protocol version: 1
Gateware version: 1
Gateware revision: 30
Gateware target: LimeSDR-Mini
Serial number: 0x1d587f46db6271
Free connection… OKpi@raspberrypi:~ $ LimeQuickTest
[ TESTING STARTED ]
->Start time: Mon Jan 4 14:39:18 2021
->LimeSuite version: 20.10.0-unknown->Device: LimeSDR Mini, media=USB 3.0, module=FT601, addr=24607:1027, serial=1D587F46DB6271, HW=3, GW=1.30
Serial Number: 1D587F46DB6271
Chip temperature: 20 C[ Clock Network Test ]
->REF clock test
Test results: 38372; 51569; 64766 - PASSED
->VCTCXO test
Results : 6710991 (min); 6711146 (max) - PASSED
->Clock Network Test PASSED[ FPGA EEPROM Test ]
->Read EEPROM
->Read data: 13 0A 15 13 0A 15 02
->FPGA EEPROM Test PASSED[ LMS7002M Test ]
->Perform Registers Test
->External Reset line test
Reg 0x20: Write value 0xFFFD, Read value 0xFFFD
Reg 0x20: value after reset 0x0FFFF
->LMS7002M Test PASSED[ RF Loopback Test ]
->Configure LMS
->Run Tests (TX_2 → LNA_W):
CH0 (SXR=1000.0MHz, SXT=1005.0MHz): Result:(-24.3 dBFS, 5.00 MHz) - FAILED
->Run Tests (TX_1 → LNA_H):
CH0 (SXR=2100.0MHz, SXT=2105.0MHz): Result:(-20.8 dBFS, 5.00 MHz) - FAILED
->RF Loopback Test FAILED=> Board tests FAILED <=
Elapsed time: 2.77 seconds
There is no sign of any physical damage (indeed the unit came to me mounted in an aluminium die-cast box for protection). Is there anything else that you would like me to try, or can you authorise an RMA?
Thanks
Dave, G8GKQ