Decoding POCSAG with GQRX and Multimon

SDR

Today, I watched this video on YouTube and was amazed how easy it is to decode POCSAG pagers.

All you need is GQRX and Multimon. The only thing the video misses is a small shell script like this

nc -l -u -p 7355 |
    sox -t raw -esigned-integer -b 16 -r 48000 - -esigned-integer -b 16 -r 22050 -t raw - |
    multimon-ng -t raw -a POCSAG512 -a POCSAG1200 -a POCSAG2400  -f alpha -

Basically, you use netcat to open a UDP server (-l = listen) and start streaming samples from GQRX by pressing this button.

You can configure the port, the one in the example is the default port of GQRX. As shown in the video, you have to use “Narrow FM” demodulator. A bandwidth of around 40k works pretty good for me. Here in Paderborn, Germany POCSAG seems to be used mainly by the ambulance.

I tested it with my Ettus B210 and my RTL SDR dongle. Both worked fine.

Have fun!