Provided by: rtl-sdr_0. bug


       rtl_fm - a simple FM demodulator for RTL2832 based DVB-T receivers


       Uses  a  re-purposed  DVB-T  receiver  as  a  software defined radio to
       receive narrow band FM signals and demodulate to audio. Written for and
       incorporated in the osmocom rtl-sdr project.

       Narrowband   FM  is  commonly  used  by  public  service  agencies  and
       commercial dispatch operations in the VHF  and  UHF  bands.   Also  can
       demodulate  Wideband  FM, as found in the 88-108 MHz FM broadcast band.
       Experimental options include AM, LSB, USB and DSB demodulation.

       Much software is available for the  RTL2832.  Most  of  the  user-level
       packages  rely on the librtlsdr library which comes as part of the rtl-
       sdr codebase. This codebase contains both the library itself and also a
       number  of  command  line tools such as rtl_test, rtl_sdr, rtl_tcp, and
       rtl_fm. These command line tools  use  the  library  to  test  for  the
       existence  of  RTL2832  devices  and  to  perform  basic  data transfer
       functions to and from the device.

       Because most of the  RTL2832  devices  are  connected  using  USB,  the
       librtlsdr library depends on the libusb library to communicate with the


       With a suitable antenna for receiving the signal attached to  the  rtl-
       sdr  supported  device, this program will output the digital audio data
       decoded from that signal. The data can be listened to by piping to  Sox
       or aplay applications to play the stream on the computer sound card.


       rtl_fm [-f freq] [-options] [filename]


       -f frequency_to_tune_to [Hz]
               (use multiple -f for scanning, requires squelch)
               (ranges supported, -f 118M:137M:25k)

       -s sample_rate (default: 24k)

       -d device_index (default: 0)

       -g tuner_gain (default: automatic)

       -l squelch_level (default: 0/off)

       -o oversampling (default: 1, 4 recommended)

       -p ppm_error (default: 0)

       -E sets lower edge tuning (default: center)

       -N enables NBFM mode (default: on)

       -W enables WBFM mode (default: off)
               (-N -s 170k -o 4 -A fast -r 32k -l 0 -D)

               (a '-' dumps samples to stdout)
               (omitting the filename also uses stdout)

Experimental options

       -r output_rate (default: same as -s)

       -t squelch_delay (default: 20)
               (+values will mute/scan, -values will exit)

       -M enables AM mode (default: off)

       -L enables LSB mode (default: off)

       -U enables USB mode (default: off)

       -D enables DSB mode (default: off)

       -R enables raw mode (default: off, 2x16 bit output)

       -F enables high quality FIR (default: off/square)

       -D enables de-emphasis (default: off)

       -C enables DC blocking of output (default: off)

       -A std/fast/lut choose atan math (default: std)

               (a '-' dumps samples to stdout)
               (omitting the filename also uses stdout)


       Produces signed 16 bit ints, use Sox or aplay to hear them.

       rtl_fm ... - | play -t raw -r 24k -es -b 16 -c 1 -V1 -
                                | aplay -r 24k -f S16_LE -t raw -c 1

       rtl_fm ...  -s 22.5k - | multimon -t raw /dev/stdin


       RTL-SDR wiki documentation:

       sox(1), play(1), aplay(1)

       Other rtl-sdr programs:

       rtl_adsb(1), rtl_eeprom(1), rtl_sdr(1), rtl_tcp(1), rtl_test(1)


       This manual page was written by Maitland Bottoms for the Debian project
       (but may be used by others).


       Copyright (c) 2013 A. Maitland Bottoms <>

       This program is free software: you can redistribute it and/or modify it
       under  the  terms of the GNU General Public License as published by the
       Free Software Foundation, either version 2 of the License, or (at  your
       option) any later version.

       This  program  is  distributed  in the hope that it will be useful, but
       WITHOUT  ANY  WARRANTY;  without   even   the   implied   warranty   of
       General Public License for more details.