If you want to listen use rtl_fm (in rtl_sdr). It's very efficient but it has no GUI for tuning. Use a GUI program to find what you want to listen to then set up some little scripts to call rtl_fm with the right frequency, mode, PPM correction, etc. I had a cron job making daily podcasts of the BBC Newshour by recording in MP3 through Sox, worked quite well. This was on a Raspberry Pi 3B. It would work fine for monitoring a repeater, just get the right squelch level by experimenting. Or any single frequency really. It's not that practical to make it scan because if you go out of a 2 MHz range you get all these delays waiting for the PLL to lock. 1 dongle per frequency or 2 MHz band might work out, not sure how you'd combine the audio. Try rtl_fm --help and study the output.
My newshour script:
BBC is rebroadcast on a local NPR FM station here late at night.
It's the flashy GUI junk that's wasting CPU because none I've seen yet use the GPU for that. Cubicsdr has several spectrum displays plus a waterfall or two going all the time, no way to turn them off. Other than that it's not too bad. It doesn't use Gnuradio like GQRX I don't think. Gnuradio has tons of Python, not very efficient.
My newshour script:
Code:
#!/bin/sh
adate=`date +"%Y-%m-%d_%H-%M"`
/usr/local/bin/rtl_fm -f 89300000 -M fm -s 190k -p 59 -r 48k - | sox -t raw \
-r 48k -b 16 -e signed-integer -c 1 -V1 - -t mp3 bbc_nh_$adate.mp3 trim 0 59:50BBC is rebroadcast on a local NPR FM station here late at night.
It's the flashy GUI junk that's wasting CPU because none I've seen yet use the GPU for that. Cubicsdr has several spectrum displays plus a waterfall or two going all the time, no way to turn them off. Other than that it's not too bad. It doesn't use Gnuradio like GQRX I don't think. Gnuradio has tons of Python, not very efficient.