Losing LNA gain

Running a LimeSDR V1.4s board in an Win7 environment with SDR-Console V3 Feb. 21 build 696 I suddenly lost about 30 dB of signal. I am using the Rx1_W input on the FM BC-band. Now the LNA gain control does not have any effect on the signal. Going from Max gain to -30 dB gain on the control lowers the signal by 2 dB at most. The weaker FM-stations has also disappeared from the band.

The Rx1_L has the same defect but Rx1_H reacts with a ~25 dB reduction of the signal.

Has anyone else experienced this?

Is it a control issue or has the LNA ceased to work?

Can Lime Suit GUI be used to diagnose the problem?

If it is a HW fault (dead LNA), is there any warranty on the LimeSDR?

Regards Ingolf, SM6FHZ

Recheck all 3 gain settings and which antenna …

Recheck how manny samples per second you set to and also check that adc low pass filter is set around 60mhz or so … not too important if yor above 30mhz Lo.

Hi Ingolf,

Is your firmware up to date? This is the latest I see.

If that looks OK, you could install HDSDR and the ExtIO_LimeSDR.dll This combination allows you to access the RX2 set of antenna connectors. See if that behaves the same…

HDSDR — http://www.hdsdr.de/
ExtIO_LimeSDR.dll — https://github.com/jocover/ExtIO_LimeSDR
Grab the link at the bottom of this page and unzip the file. Then put it in the same directory as HDSDR.


Thanks to all for your suggestions. I have checked on them but without a positive result.

Mike; the Device Info is exactly as in you example.

To be more clear, the gain was OK from the start but it suddenly went down by 20 to 30 dB in RX1_W and RX1_L. RX1_H seems to be less affected (I have no good reference there). I did not do any specific maneuvering at the time for the loss of gain.

I am trying to understand if it is a control issue or a HW failure issue.

I am not sure what I can see and do with the Lime Suite GUI controls. Maybe there is a possibility to read or check if something is different from what it should be vi this GUI. So far I have not found anything that makes a difference there.

/ Ingolf

Was the noise floor before the drop around -70db or -110db ?

If it was -70db and dropped to -110, i think it is a sign of a SoapySDR bug that shows once in a while in Linux/Ubuntu/Gqrx…

I would suggest tuneing above 30Mhz and adjust the samples/sec any where from 1,000,000 to 10,000,000.

I no longer can set a working S/sec of 1,000,000 or lower and have anythig shown where it should be below 24.5Mhz or so … i forget.

I stick to around 5,000,000 samples/sec and use decimation to reduce the CPU workload … USB throughput around 400K/sec … around 800K/sec studders and 150K/sec crashes.