Hi, I noticed an issue when making the limefm application. My WBFM Spectrum is poluted with a lot of GSM / LTE Images. I don’t recall that happening when I first tested my limesdr (I think about a year ago), so it might be an issue with the latest firmware.
I’m using the LNAL from Channel A and unplugged all other antenas just in case. My Antena is tuned to 2m band so it should receive FM signals better than GSM band. Also my other sdrs (RTLSDR, Airspy) can receive FM without a antenna plugged in.
So I run LimeQuickTest and it gave me an error:
┌─[lucas@nblucas] - [~] - [Sun Sep 02, 18:00]
└─[$] <> LimeQuickTest
[ TESTING STARTED ]
->Start time: Sun Sep 2 18:00:40 2018
->Device: LimeSDR-USB, media=USB 3.0, module=FX3, addr=1d50:6108, serial=0009062000C5170C
Serial Number: 0009062000C5170C
[ Clock Network Test ]
->FX3 GPIF clock test
Test results: 14682; 18438; 22194 - 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
->VCTCXO test
Results : 5112944 (min); 5113077 (max) - PASSED
->ADF4002 Test
Result: 10 - PASSED
->Clock Network Test PASSED
[ FPGA EEPROM Test ]
->Read EEPROM
->Read data: 11 05 0F 11 05 0F 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:(-14.0 dBFS, 5.00 MHz) - PASSED
CH1 (SXR=800.0MHz, SXT=805.0MHz): Result:(-15.8 dBFS, 5.00 MHz) - PASSED
->Run Tests (TX_1 -> LNA_W):
CH0 (SXR=1800.0MHz, SXT=1805.0MHz): Result:(-15.0 dBFS, 5.00 MHz) - PASSED
CH1 (SXR=1800.0MHz, SXT=1805.0MHz): Result:(-27.4 dBFS, 5.00 MHz) - FAILED
->Run Tests (TX_2-> LNA_H):
CH0 (SXR=2500.0MHz, SXT=2505.0MHz): Result:(-17.8 dBFS, 5.00 MHz) - PASSED
CH1 (SXR=2500.0MHz, SXT=2505.0MHz): Result:(-15.8 dBFS, 5.00 MHz) - PASSED
->RF Loopback Test FAILED
=> Board tests FAILED <=
Elapsed time: 1.42 seconds
I’m using Gateware 17 revision 2.
Any ideas what can be the cause of the issues?
EDIT: Same band with lower gains:
Same band with Airspy Mini:
EDIT2:
Ok so I changed the antenna between my 2m band antenna and a Baofeng UV-5R antena (which works for FM, VHF and UHF) and the images are bit less noticiable. If I put the antena in certain position, it disappears by complete:
That also causes the SNR of the WBFM stations to be higher (I think the GSM stuff is overloading the frontend). I tried to set the analog filter to something low (like 2MHz), but even so I can see the GSM Images. Is there anything else I can do?
EDIT3: Just for reference, an image at same center frequency as before: