You're all correct, except there are not that many $30 SDRs out there. Most of them start at around $200 and end in very very high thousands. Also, most SDRs ha

You're all correct, except there are not that many $30 SDRs out there. Most of them start at around $200 and end in very very high thousands. Also, most SDRs have clearly superior capabilities to the RTL-SDR, though often those capabilities are not required. BTW, for simple AM/FM demodulation I cannot recommend enough the handy https://github.com/charlie-foxtrot/RTLSDR-Airband https://github.com/charlie-foxtrot/RTLSDR-Airband. Most of the LiveATC.net feeds run on it, for example. It can be used for any AM/FM audio, for any number of simultaneous channels, even on a weak machine like a raspberry pi.