Multi-channel narrow-band FM recorder for GNU Radio

Author: Louis Brown, KD4HSO

Features:

• Parallel demodulation and recording of NBFM radio channels
• Up to N channels limited by CPU and bandwidth of SDR (tested to 25 MHz)
• Squelched audio blocked from recording
• Mixed audio for real-time monitoring
• Channels recorded to individual *.wav files

Tested with:

• GNU Radio 3.7
• Ettus N210 + WBX
• Ettus B200

Notes:

Run with -h for help

Channels (in Hz) are read from channels.txt newline delimited file. Suggest starting with 162.55E6 for local NOAA radio or 144.39E6 for APRS.

Keep adding channels as long as they are within the 25 MHz sample rate supported by the USRP, and your processor can handle the load. Running volk_profile will make a big difference.

May need to adjust the gain and squelch values depending on the hardware.

Use with the Ettus N210 + WBX: ./nbfm_rec.py --args="addr=168.1.13" --gain=10 -v

Use with the Ettus B200: ./nbfm_rec.py --args="type=b200, master_clock_rate=25E6" --gain=50 -v

Note the program was developed with the N210 which has a maximum bandwidth of 25 MHz, therefore the B200 master clock should be set to 25E6.

nbfm_rec_diagram.asciio is the ASCIIO block diagram