New method for generating wideband spectograph’s with Radio-Sky and an RTL-SDR

Radio-Sky Spectrograph is a software application that is designed to produce waterfall displays similar to other software, but with a focus on observing radio astronomy phenomena. 

Radio-Sky Spectrograph displays a waterfall spectrum. It is not so different from other programs that produce these displays except that it saves the spectra at a manageable data rate and provides channel widths that are consistent with many natural radio signal bandwidths. For terrestrial, solar flare, Jupiter decametric, or emission/absorption observations you might want to use RSS [Radio-Sky Spectrograph].

Last year, we posted about the release of RTL_Bridge, which is a program designed to interface an RTL-SDR dongle with Radio-Sky Spectrograph. One limitation with RTL_Bridge was that it was limited to the dongles maximum bandwidth of about 2.4 MHz. Now Raydel Abreu Espinet (CM2ESP) has written a new application called RTL-WideSpectrum which allows for wideband spectral sweeps in Radio-Sky Spectrograph by using the RTL-SDR to quickly switch between frequencies and combine the outputs. It is similar to how rtl_power works.

With RTL-WideSpectrum and Radio-Sky Spectrograph, Raydel was able to capture this solar burst shown below which occurred between 28-48 MHz.

A solar burst between 28 - 48 MHz captured with an RTL-SDR dongle, RTL-WideSpectrum and Radio-Sky Spectrograph.
A solar burst between 28 – 48 MHz captured with an RTL-SDR dongle, RTL-WideSpectrum and Radio-Sky Spectrograph.


  1. klaus

    all of these wideband scanners have these bars in between, this is because of a lower sensitivity at the beginning and end of bandwidth.
    why not use only one 2 MHz portion out of the 2,4 MHz ??
    must explain this:
    for a scan from 20 MHz they tune from 20 to 22,4 – next would be 22,4 to 24,8 – and so on…
    why not tune from 20 to 22 and use only 2 MHz, next 22 to 24 and 24 to 26 – so those 0,2 MHz at the beginning and end are forgotten ?

    • admin

      rtl_power can do this with the crop feature, and using crop is recommended. I guess it’s just not implemented yet in RTL-WidebandScanner.

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