LimeSDRmini with Soapy-Interface: S/N could be better

#1

System: Linux. (OpenSuse)
Software: Soapy, built from sources, Release 0.8.0
LimeSuite built from sources, Release 19.01.0

Own Software for RX, Started from Part8 of the LimeSDR made simple Examples.
Steps after Start of the RX:

  • Init Mini
  • Set Samplingrate 1.536 S/s
  • Set Center Frequency to 132800kHz, Split in 100kHz BB and 132700kHz RF
  • Calibrate RX with LPF BW=2.5MHz
  • Enable GFIR with BW 70kHz
    -Set LNA to 10
    -Set TIA to 12
    -Set PGA to 14.
  • Set LPF BW=1.401MHz.
    -Setup Stream C32-Samples per Bunch
  • Start thread with a loop:
    to get the with 16384 Samples per request.
    - decimate these 16384 Samples by 16 to get 96000S/s
    which are then sent over UDP to another program for demodulation etc.
    End loop

When demodulating aircraft AM-Transmissions (e.g. 132816.9kHz), the S/N is not convincing. (AM carrier at -90dBm, but modulation near the -120dBm-Noise floor), hard to understand.

I made a comparison with the RTL-Stick (Osmocom) on Win-XP with HDSDR.
In this program I can very clearly hear the tower and the aircrafts.

I thing, that my Soapy-Settings are not ok for the Mini. (But the Image-Suppression is very good).

Are there any suggestions, what could increase the RX-Quality?