Yeah, sdrtrunk is useless so far except for trunking, and I couldn't make it work with the trunking brand around here. Conventional is on their list of features to add but they have some weird schedule of what they're going to add when. I was surprised at the speed and efficiency though for something written in Java.
qtcsdr has no squelch, or a way to enter your dongle's ppm value. For plain old FM wideband broadcast it works OK.
Mostly I use rtl_fm, I have a little collection of scripts I've written for it. The -p argument is the ppm, the -l is squelch level. Squelch on am is very different from squelch on nbfm.
Most recent first. I bought some frs/gmrs walkie talkies and want to survey how busy the channels were around here. So this is nbfm and scanning:
Code: Select all
#!/bin/bash
# sox isn't verbose in this version
# frs (Family Radio Service):
rtl_fm -l 132 -M fm -p 59 -f 462562500 -f 462587500 -f 462612500 \
-f 462636500 -f 462662500 -f 462687500 -f 462712500 -f 462562500 \
-f 462587500 -f 462612500 -f 462637500 -f 462662500 -f 462687500 \
-f 462712500 \
# gmrs:
-f 462550000 -f 462575000 -f 462600000 -f 462625000 \
-f 462750000 -f 462700000 -f 462725000 - | play -t raw -r 24k \
-e signed-integer -b 16 -c 1 -
For using rtl_tcp on a local wbfm station:
Code: Select all
#!/bin/bash
rtl_tcp -a 192.168.0.16 -d 0 -g 20.7 -f 88500000
The same for a nbfm weather frequency
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#!/bin/bash
rtl_tcp -a 192.168.0.16 -d 0 -g 40 -f 162400000
I was using rtl_tcp to get a stream of I/Q values for something I was writing, then I switched to using librtlsdr so I had more control over it. rtl_tcp also works with HDSDR as a remote input over a LAN.
For LoJack, I'm not sure this worked. I haven't use multimon before, it's supposed to decode things like packet radio. Turns the audio into text on your screen.
Code: Select all
#!/bin/sh
# Trying to decode Lojack, 1200 baud at 173.075
rtl_fm -M fm -p 59 -f 173075000 \
- | multimon -v 10 -t raw -a SCOP
Records an hour from a local FM station which relays the BBC's Newshour, saves as an MP3 podcast sort of thing. I can call it from a cron job to run at a certain time of day.
Code: Select all
#!/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_$adate.mp3 trim 0 59:50
Records nbfm from 854.490000 MHz, saves as an MP3. Just ctrl-C it to quit. Some at least of these will compress radio transmissions by not recording dead air time. If you're in western Massachusetts this frequency is state-wide state police via linked repeaters. Interesting, I heard them catching the Boston Bomber on it, and that's 3 hours from here.
Code: Select all
#!/bin/bash
datestr=`date +"%Y-%m-%d_%H-%M"`
outname=sp_$datestr.mp3
rtl_fm -l 132 -M fm -s 24k -p 58 -f 854490000 - \
| sox -traw -r24k -es -b16 -c1 -V1 - -tmp3 $outname
Scans a bunch of Massachusetts state police frequencies
Code: Select all
#!/bin/sh
# sox isn't verbose in this version
rtl_fm -l 132 -M fm -p 59 -f 854040000 -f 854240000 -f 854315000 -f 854415000 \
-f 854490000 -f 854540000 -f 855165000 -f 855240000 -f 858790000 -f 867350000 \
-f 867715000 - | play -t raw -r 24k -e signed-integer -b 16 -c 1 -
Sweeps the 118 - 137 MHz aircraft (AM) band. Squelch is funky, I've also used -l 45
Code: Select all
#!/bin/sh
rtl_fm -M am -f 118M:137M:25k -p 59 -s 24k -l 10 - | \
play -t raw -r 24k -e signed-integer -b 16 -
Does basically the same thing but feeds MP3 audio out tcp port 8080
Code: Select all
#!/bin/sh
rtl_fm -M am -f 118M:137M:25k -p 59 -s 24k -l 45 \
- | sox -traw -r24k -es -b16 -c1 -V1 - -tmp3 - | socat -u - TCP-LISTEN:8080
The other half is to use something like netcat piped into sox. It came from one of Kyle Keen's pages about rtl_fm. I'm not finding the script I used for decoding back into audio.
This is just a simple nbfm monitor of 162.425 MHz. A local automated weather transmitter.
Code: Select all
#!/bin/bash
rtl_fm -M fm -S -l 132 -p 58 -f 162425000 - | play -t raw -r 24k \
-e signed-integer -b 16 -c 1 -
rtl_fm changed the way they specify the demodulation, I have both the new and old versions around. -M am or -M fm is the new way (can also do usb and lsb) but I thought I saw the old way in one of these.
https://en.wikipedia.org/wiki/The_Bell_Curve Nevermind that last link, it's not relevant. 
