rtl_fm scanning

Ben Moore benjamin.n.moore at gmail.com
Sun Feb 24 10:15:12 UTC 2013

I am having a problem with using multiple frequencies with rtl_fm.  Single frequencies work just fine.

For example:

rtl_fm -f 462.5625M -f 462.5725M -N -s 12k -r 12k -g 48 -l 50 | play -r 12k -e signed-integer -b 16 -t raw -c 1 -V1 -

Will get to:

Sampling at 1008000 Hz.
Output at 12000 Hz.
Exact sample rate is: 1008000.009613 Hz
Tuner gain set to 48.00 dB.

Then freeze.

If I set the squelch low enough, it will continuously monitor the first channel.  If I have a transmitter on before starting the command, it will monitor that.  But when the transmitter turns off, rtl_fm hangs.  I looked at the code but couldn't fix it.  Maybe it's some reset command that's not being done between frequencies. If I force "data_ready" to unlock, it scans, but there's no data.  Although, rtl_tcp works just fine when connecting with SDR# and changing frequencies.

This is on a Raspberry Pi btw, latest rtl-sdr source code.  Sorry if this has already been discussed somewhere, I could not find it.

- Ben

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