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rtl_fm issues decoding pocsag/flex with multimon-ng

Posted: Fri Jan 22, 2021 6:54 pm
by BrokenSolenoid
I have the standard rtl-sdr.com dongle. After multiple attempts at decoding pocsag i simply piped it threw netcat and was amazed it worked

So nc -l -u 7355 | sox -r 48000 -t raw -b 16 -c 1 -e signed-integer /dev/stdin -r 22050 -t raw -b 16 -c 1 -e signed-integer - | multimon-ng -t raw -c -a POCSAG512 -a POCSAG1200 -a POCSAG2400 -a FLEX -a SCOPE -f alpha /dev/stdin
Will work perfectly when i have gqrx running and lock onto the frequency (932.287.100)

But when i try with rtl_fm: rtl_fm -d 0 -E dc -F 0 -A fast -f 932.287M -s22050 - | multimon-ng -q -b1 -c -a Flex -a POCSAG512 -a POCSAG1200 -a POCSAG2400 -f alpha -t raw /dev/stdin ** even changing the frequency to 932287100 does nothing rtl_fm simply sits there showing nothing **

Heres my terminal output.
Found 1 device(s):
0: Realtek, RTL2838UHIDIR, SN: 00000001

Using device 0: Generic RTL2832U OEM
Detached kernel driver
Found Rafael Micro R820T tuner
Tuner gain set to automatic.
Tuned to 932639800 Hz.
Oversampling input by: 64x.
Oversampling output by: 1x.
Buffer size: 5.80ms
Exact sample rate is: 1411200.013458 Hz
Allocating 15 zero-copy buffers
Sampling at 1411200 S/s.
Output at 22050 Hz.

It seems to tune at 932639 even though i set it to 932.287M or 932287100. The output listed will not change nothing will occur even though if i was to run the same frequency on GQRX and udp to netcat i could decode everything.