RTLSDR-Airband VS trunk-recorder

You're all correct, except there are not that many $30 SDRs out there. Also, most SDRs have clearly superior capabilities to the RTL-SDR, though those capabilities often are not required.

BTW, for simple AM/FM demodulation I cannot recommend enough the handy https://github.com/charlie-foxtrot/RTLSDR-Airband. For example most of LiveATC.net feeds run on it.

rtlsdr_airband, but again requires knowing the frequencies of interest ahead of time.

You may want to give RTLSDR-Airband a look. Its designed for analog AM/NFM voice traffic and can be configured to operate on any frequency your rtlsdr dongle can handle. It can also be configured to output to an mp3 file, in addition to other things like IceCast.

There’s an example service config file in the repo: https://github.com/charlie-foxtrot/RTLSDR-Airband/blob/main/init.d/rtl_airband.service

I have been streaming the output from RTLSDR-Airband (https://github.com/charlie-foxtrot/RTLSDR-Airband) with icecast2 for several (5?) Years now, and I have some time and inclination to look at reducing latency (currently best is 10s, but often much more.)

https://github.com/szpajder/RTLSDR-Airband Might be what you are looking for, although I don't know the performance requirements. It has a scan mode detailed here: https://github.com/szpajder/RTLSDR-Airband/wiki/Configuring-channels-for-scan-mode

If your area is P25, then https://github.com/robotastic/trunk-recorder with https://github.com/chuot/rdio-scanner makes a great setup.

Looks like its available for mac aswell. I think I can use this solely for listening and recording https://github.com/robotastic/trunk-recorder

I would search the issues on GitHub and possibly submit an issue if you don't find the answer that way. https://github.com/robotastic/trunk-recorder/issues

trunk-recorder can do this https://github.com/robotastic/trunk-recorder while originally designed for trunked systems, it can handle conventional systems as well. Which pairs nicely with https://github.com/chuot/rdio-scanner which provides a nice web/phone app interface to listen to, that includes the ability go back thru a call archive.

I've toyed with monitoring the Portland system using GitHub - robotastic/trunk-recorder: Records calls from a Trunked Radio System (P25 & SmartNet), which can monitor and record all calls, and yeah, it puts out so many messages even in normal times. And even without PPB dispatch and one of the voice frequencies, I think I got GBs of audio per day.

Trunk Recorder GitHub repository (software used to capture and record calls)

I'm using this open source project https://github.com/robotastic/trunk-recorder to do the recording, but here is a screenshot of GQRX to give you an idea of how software radio works- instead of hardware designed to listen to one channel, it samples a big chunk of the spectrum and then uses software to "tune" the individual channels- so it can listen to everything at once, no need to channel-hop, etc.