Using LimeSDR as a signal generator and spectrum analyzer

Hello everyone,
I’m quite new to SDR, so this may be an obvious question. I don’t have a spectrum analyzer, but I’d like to analyse the signal generated when transmitting from the lime. I recently watched this video using satsagen with the Pluto: Spectrum Analyzer and Tracking Generator with Pluto SDR - YouTube

My understanding is that satsagen does not support the lime, but I was wondering if I could do something similar using qspectrumanalyzer or lime suite tools shown here LimeSDR - All-in-One Lab and GNU Octave | Crowd Supply.

If I understand correctly, it would not have the tracking generator that satsagen has, but could I just tell the lime to transmit a certain signal, connect the tx to rx (with proper attenuation) and read the resulting spectrum?

Thanks for your help,

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I remember seeing something in this thread, never tried it but maybe this is what you want -

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Thanks, I’ll take a look.

Hi There,

This may be far from finished, but if you are interested in a way to make a Spectrum Analyzer work based on the limesuite C API, feel free to check out my repo:
Its still a work in progress and the GUI is yet to be implemented, and more features to be added. But it should be good for playing around a bit and plotting some frequency spans already.


@gmcsor Depending on your needs, you may be able to just use GnuRadio Companion or Pothos Flow.

You should be able to create a flow graph with your Lime as

  • a source (ie transmitter), reading a file containing your signal, or using the available blocks to create the signal
  • a sink (ie receiver), displaying the spectrogram/waterfall

The LimeSDR-USB can have different sampling rates for RX and TX but are not completely unrelated (basically you can have TX = RX / 2^n, see Link between RX and TX sampling rates for more, but I recall also having issues in some cases). It can have completely different frequencies though.

I think with the LimeMini the RX and TX sampling rates must be the same.

Hi Grant
It is certainly possible to use the LimeSDR as an effective spectrum analyzer. Take a look at this simple solution using a Raspberry Pi 3 and a 7 inch touchscreen: Portsdown Band Viewer

All the source code is available on GitHub: Portsdown 2020 Band Viewer source

Dave, G8GKQ

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