I was testing the TX capability of my LimeSDR using SDRAngel, when I noticed that my output signal level had suddenly dropped, but was still barely audible. I was transmitting NBFM on VHF with a pigtail antenna connected to TX_1_1, monitoring it using a Yaesu FT-7800 transceiver. First I suspected the settings, but when I switched to TX_2_1 the signal level was OK. To check if anything was wrong I ran LimeQuickTest, it failed in the loopback test with TX_1 CH0 (which is TX_1_1, right?), see output below. Something is clearly wrong with this output, since the signal level is about 30 dB lower than in the other loopback tests. The results are consistent when I re-run the test.
Is my TX_1_1 output pin broken, or could it also be some component in the RF chain between the LMS7002 and th uFL connector? Is there anything I could measure to check what is wrong? Any other tests I could run?
[ TESTING STARTED ] ->Start time: Tue Nov 13 21:19:47 2018 ->Device: LimeSDR-USB, media=USB 3.0, module=FX3, addr=1d50:6108, serial=0009060B00473622 Serial Number: 0009060B00473622 [ Clock Network Test ] ->FX3 GPIF clock test Test results: 19369; 23125; 26881 - PASSED ->Si5351C test CLK0: 17554 / 17554 - PASSED CLK1: 17554 / 17554 - PASSED CLK2: 17554 / 17554 - PASSED CLK3: 17554 / 17554 - PASSED CLK4: 17554 / 17554 - PASSED CLK5: 17554 / 17554 - PASSED CLK6: 17554 / 17554 - PASSED ->ADF4002 Test Result: 10 - PASSED ->VCTCXO test Results : 5112921 (min); 5113049 (max) - PASSED ->Clock Network Test PASSED [ FPGA EEPROM Test ] ->Read EEPROM ->Read data: 11 01 13 11 01 13 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_L): CH0 (SXR=800.0MHz, SXT=805.0MHz): Result:(-14.8 dBFS, 5.00 MHz) - PASSED CH1 (SXR=800.0MHz, SXT=805.0MHz): Result:(-17.4 dBFS, 5.00 MHz) - PASSED ->Run Tests (TX_1 -> LNA_W): CH0 (SXR=1800.0MHz, SXT=1805.0MHz): Result:(-56.0 dBFS, 5.00 MHz) - FAILED CH1 (SXR=1800.0MHz, SXT=1805.0MHz): Result:(-19.6 dBFS, 5.00 MHz) - PASSED ->Run Tests (TX_2-> LNA_H): CH0 (SXR=2500.0MHz, SXT=2505.0MHz): Result:(-16.7 dBFS, 5.00 MHz) - PASSED CH1 (SXR=2500.0MHz, SXT=2505.0MHz): Result:(-16.1 dBFS, 5.00 MHz) - PASSED ->RF Loopback Test FAILED => Board tests FAILED <= Elapsed time: 1.51 seconds