RTL-SDR: rtl-fm
Sumber: http://kmkeen.com/rtl-demod-guide/
FM
apt install sox rtl_fm -M wbfm -f 92.0M | play -r 32k -t raw -e s -b 16 -c 1 -V1 -
rtl_fm -f 92.0M -M fm -s 170k -A fast -r 32k -l 0 -E deemp | play -r 32k ...
'-f ...' indicated the frequency to tune to -M fm means narrowband FM -s 170k means to sample the radio at 170k/sec -A fast uses a fast polynominal approximation of arctangent -r 32k means to lowpass/resample at 32kHz -l 0 disables squelch -E deemp applies a deemphesis filter
Police Scanner
rtl_fm -M fm -f 154.42M -f 154.75M -f 154.82M -f 154.89M -s 12k -g 50 -l 70 | play -r 12k -t raw -e s -b 16 -c 1 -V1 -
This one will take a lot more fiddling to work properly. First, you of course need channels used by your municipality. And this will only work if your local services have not upgraded to P25 or some other trunked system.
-M fm narrowband FM -f ... frequency to tune, use multiple times for scanning -s 12k sample rate, about as narrow as possible for FM voice -g 50 set gain to maximum (use a value appropriate to your dongle) -l 70 set squelch to 70. The exact values varies a lot. Changing the gain or sample rate will require a change in the squelch to compensate.
AirBand Scanner
rtl_fm -M am -f 118M:137M:25k -s 12k -g 50 -l 280 | play -r 12k -t raw -e s -b 16 -c 1 -V1 -
rtl_fm -M am -f 118M -f 120M -f 128.8M -f 119.7M -s 12k -g 30 -l 300 | play -r 12k -t raw -e s -b 16 -c 1 -V1 -
-M am AM demodulation -f start:stop:interval a range of frequencies to scan -s 12k same as above -g 50 same as above -l 280 squelch level, exact value varies a lot