https://www.rtl-sdr.com/
https://wiki.radioreference.com/index.php/Software_Defined_Radios
https://swling.com/blog/2018/09/software-defined-radio-primer-part-1-introduction-to-sdrs-and-sdr-applications/
https://wiki.radioreference.com/index.php/SDRs_for_Amateur_Radio_Use
https://wiki.radioreference.com/index.php/SDR_Software_Applications
http://kiwisdr.com/public/
http://rx.linkfanel.net/
http://websdr.org/