Poor Mans Spectrum Analyzer with an RTL-SDR and Noise Source

Over on YouTube channel Bootstrap Workbench has been running a series on using an RTL-SDR and noise source to create a poor man’s spectrum analyzer. So far he has three videos available. The first shows how to install and setup Spektrum, his preferred Windows based wideband scanner for the RTL-SDR.

The second video shows how the RTL-SDR, noise source and Spektrum can be used to tune a cavity duplexer. A cavity duplexer is an adjustable set of filters that allows you to use a single antenna for TX and RX at different frequencies. It can be tuned by adjusting screws on the unit body.

In the third video he shows how to examine the response of a dual ferrite isolator/circulator which is a device that can be used to ensure RF only travels in one direction. This could be use for example to prevent damage to a TX power amplifier from reflected signals due to high VSWR or other nearby powerful signals.

Poor Man's Spectrum Analyzer - Installing Spektrum and Testing an RTL-SDR com 88-108 Bandstop Filter

Poor Man's Spectrum Analyzer - Tuning Cavity Duplexers

Poor Man's Spectrum Analyzer - Examining a Dual Ferrite Isolator/Circulator

If you’re interested in this we also have our own tutorial available about setting something like this up, but using alternative software.


  1. Roger

    I would call this a Network Analyzer not a Spectrum Analyzer function. A Spectrum Analyzer can perform such measurements in operational tests and with calibration and correction make absolute power measurements. RTL-SDR requires an external calibrator for that function.

  2. Rob

    How easy would it be to use this as an antenna analyzer? would it just be a case of getting and SWR bridge and connecting: noise source to the input, RTL-SDR dongle to the output and the antenna to the DUT port? Would the -db scale down the left hand side be enough to work out the return loss and therefore calculate SWR?

  3. Bootstrap Workbench

    Thanks for the coverage of my videos! In addition to these videos, I have amateur radio repair and tutorial videos, vintage test equipment repair videos and more. More videos regarding the RTL SDR are coming soon, so make sure to like, share and subscribe.

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