Loopback test failing

Projects LimeSDR
1

I’ve had my lime mini for a couple of months. All I’ve done with it so far is some basic ISM receiving.

Today I updated the firmware using LimeUtil, and afterwards I decided to run LimeQuickTest. Should I be worried about the failed loopback test?

LimeQuickTest
[ TESTING STARTED ]
->Start time: Thu Oct 11 21:15:04 2018

->Device: LimeSDR Mini, media=USB 3.0, module=FT601, addr=24607:1027, serial=1D40E150A83D23
Serial Number: 1D40E150A83D23

[ Clock Network Test ]
->REF clock test
Test results: 48560; 61757; 9418 - PASSED
->VCTCXO test
Results : 6711043 (min); 6711203 (max) - PASSED
->Clock Network Test PASSED

[ FPGA EEPROM Test ]
->Read EEPROM
->Read data: 12 06 1B 12 06 1B 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:(-27.4 dBFS, 5.00 MHz) - FAILED
->Run Tests (TX_1 → LNA_H):
CH0 (SXR=2100.0MHz, SXT=2105.0MHz): Result:(-15.3 dBFS, 5.00 MHz) - PASSED
->RF Loopback Test FAILED

=> Board tests FAILED <=

Elapsed time: 2.52 seconds

2

Hi, @ryansuchocki

Have you retried loopback tests? Does it always fail?

3

Yes. The TX_2 test fails consistently at around -27dBFS.

4

Are you running test with antennas connected? Loopback test results are more reliable if you run it without antennas connected.
Your signal level on TX_2->LNA_W loopback test is ~10db lower than it should be. It indicates that there may be some damaged component on TX_2 or LNA_W path and you get lower output level (TX_2) or lower sensitivity (LNA_W).

5

I have always run the loopback tests without antennas.

Can someone give me an example of the absolute amplitude out of TX_2 (or the absolute sensitivity into LNA_W) at 1000MHz on a working unit, so I can know for sure which path is compromised?