RTL-SDR As a Spectrum Analyzer

Hackaday has brought to attention a blog post by Kerry Wong which shows how the RTL-SDR can be used as a simple and inexpensive spectrum analyzer. In the past we’ve already posted numerous examples of the RTL-SDR being used as a spectrum analyzer but Kerry’s post discusses some of the do’s and don’ts that you need to think about when using a SDR as a spectrum analyzer and also provides some measurements.

During his tests he discovered that popular software like RTLSDR Scanner and SDR# either distort the spectrum or don’t display the signal amplitude correctly. Only GQRX and osmocom_fft seemed to give an accurate depiction of the spectrum.

Kerry also discusses how to calibrate the spectrum display to show proper power levels, how to set the gain for spectrum analysis and discusses some thoughts on LO leakage.

Using an RTL-SDR as a spectrum analyzer with osmocom_fft
Using an RTL-SDR as a spectrum analyzer with osmocom_fft


  1. mini

    I m looking for project that involves spectrum analysis and deciding proper modulation blocks based on the results obtained from GNU radio using machine learning/

  2. Cato Andrè Pettersen

    Hi, i am desperatly looking for a RADIO NETWORK ANALYZER,
    and wondering about, is there a way to use RTL-SDR as this?

    • Steve

      I assume you mean a vector RF network analyzer (VNA). A device used to determine return loss ratio, insertion loss, impedance measurements across a given bandwidth, distance to fault (Time Domain Reflectometer – TDR), among others. To perform these measurements test signals are provided by a tracking generator driving the DUT. The generator sweep is synced with a signal from the analyzer so the generator freq “tracks” with the analyzer. Many spectrum analyzers have this capability and require a signal from the analyzer to control the generator frequency. SAs can perform some of the same measurements as a VNA, although cumbersome. I use a Copper Mountain USB connected VNA. Search for info on RF vector analysis, Smith chart, TDR, antenna impedance matching. It would be interesting to see if the RTL engineers could provide the hardware functionality since entry level VNAs start at around $4000.

  3. superUser1

    Can I use RTL based DVB-T stick to watch DVB-C (digital cable TV) ?
    I think RTL devices suffer from limited bandwidth.
    linuxtv.org wiki page for DVB-C USB devices lists some DVB-T devices.
    Is it posible to watch digital cable (SD or HD channels) using SDR software ?

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