SO# 545983 - LIME SDR Mini - Carrier signal not supressed. Caused by a defective filter?

Hello,
can you possibly help with the following issue regarding a problem with the LIMESDR Mini (P/N: cs-lime-05)?
Our customer states:

Shortly after the start of the transmission, the modulation completely disappears both in the transmit
signal and in the receive signal.
I use the Lime SDR in mode SSB USB at 432Mhz. Here the carrier signal is not suppressed and is sent out with. Furthermore there are remains of the useful signal in the LSB.
It seems to me that a filter does not work.

Can you please advise if this could be a defect? What other details would be needed to look into this problem?

thank you very much.
Best regards
Adnan

1 Like

Hi Adnan,

It’s going to be best if you could have the customer post here direct. Would likely prove far more difficult to resolve with a third party in the middle acting as a proxy.

Hi there,

what’s your answer? Is the filter broken? or is there a way to solve the problem?

You’d need to provide more information, such as what application you are using and details of the settings.

Also if you could please run LimeQuickTest and post the results.

[ TESTING STARTED ]
->Start time: Tue Jan 7 17:06:16 2020

->Device: LimeSDR Mini, media=USB 2, module=FT601, serial=1D4257CBE603F3, index=0
Warning: USB3 not available
Serial Number: 1D4257CBE603F3

[ Clock Network Test ]
->REF clock test
Test results: 57236; 4897; 18094 - PASSED
->VCTCXO test
Results : 6711027 (min); 6711183 (max) - PASSED
->Clock Network Test PASSED

[ FPGA EEPROM Test ]
->Read EEPROM
->Read data: 12 07 1B 12 07 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:(-14.6 dBFS, 5.00 MHz) - PASSED
->Run Tests (TX_1 -> LNA_H):
CH0 (SXR=2100.0MHz, SXT=2105.0MHz): Result:(-15.9 dBFS, 5.00 MHz) - PASSED
->RF Loopback Test PASSED

=> Board tests PASSED <=

Elapsed time: 4.96 seconds

Hi there,

I use the SDR Console as software on the PC. I have a 2nd Lime SDR that works fine. The emitted signal can be seen in the waterfall of the SDR Console. You can also see the carrier signal and the signal residues in the LSB.

It’s passed all the hardware tests, but would note that ideally you should use a USB 3.0 port and not USB 2.0.

Are you saying that you have two LimeSDR Mini boards, which when using with the same computer and application, you are getting different results? If so, the only other thing that comes to mind is to make sure the latest/correct gateware is loaded. You can do this by running LimeUtil --update.

SDR Console generate SSB signal without NCO oscillator. LSB image and Local oscillator are visible in the band (bump in the middle of the screen-oscillator leakage). With automatic TX calibration they must be suppressed 40dB or more. If you want spurios free signal use NCO algorhitm and selective BPF between Mini TX out and final PA stage (set NCO 10-15MHz above or below TX freq, 2MHz BPF it is not difficult to make). Anyway, it is external software issue and nothing to do with LimeSDR Mini!

Yes, I have 2 LimeSDR on the same computer with the same software and I see and hear different output signals. Both Lime SDR have the same firmware.

limesdr3

limesdr4

this is how the signal looks without modulation.

In your first post you wrote " I use the Lime SDR in mode SSB USB at 432Mhz.’
In theory SSB signal without modulation do not exist! In practice you can hear only microphone preamp. noise. Suppressed images are at least 40dB down (additional IQ image correction will add additional 20dB-all done in software).
Your posted image is confusing: is this from Oscar 100 satellite? What exactly are we watching?

sorry I’m trying to analyze a problem with a technician.

If you run a LimeQuickTest on the other LimeSDR-mini
Does it also say:
->Device: LimeSDR Mini, media=USB 2, module=FT601, serial=0123456789ABCDE, index=0
Warning: USB3 not available

And if you physically swap the devices to each others USB port, does the problem follow the device or stay with the same USB port.

1 Like

As I mentioned before, I’m trying to solve a technical problem with a Myriad RF technician. comments from others just waste my time. The problem does not come from the USB port. it is a problem in the NF or HF range of the Lime SDR. I have 2 Lime SDR. The problem only occurs with one.

With all due respect, this is a community support forum and how open source communities work — with other members just trying to help and so if you could please remain courteous.

As noted, your hardware is passing the self-test diagnostics and this does look like it could be a software problem.

Hi @Immo,

Answer the question from @mzs please:

Try it using USB3 port instead of USB2 too.

Yes, I have already done so. with the same result. I will then post it here. I also used another PC. Completely re-installed OS and application

YES, the same message appears on the other device. of course not at the USB 3 port.
But what I’m wondering is what result did you expect?

The problem comes from the NF HF side. I have no problem with USB. Can you help and explain why you are investigating the USB interface?

[ TESTING STARTED ]
->Start time: Sun Jan 19 15:19:03 2020

->Device: LimeSDR Mini, media=USB 3, module=FT601, serial=1D4C2C69DD6F61, index=0
Serial Number: 1D4C2C69DD6F61

[ Clock Network Test ]
->REF clock test
Test results: 2641; 15838; 29035 - PASSED
->VCTCXO test
Results : 6711074 (min); 6711231 (max) - PASSED
->Clock Network Test PASSED

[ FPGA EEPROM Test ]
->Read EEPROM
->Read data: 13 02 0C 13 02 0C 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:(-13.6 dBFS, 5.00 MHz) - PASSED
->Run Tests (TX_1 -> LNA_H):
CH0 (SXR=2100.0MHz, SXT=2105.0MHz): Result:(-14.2 dBFS, 5.00 MHz) - PASSED
->RF Loopback Test PASSED

=> Board tests PASSED <=

Elapsed time: 3.91 seconds