Guide to decoding POCSAG on Linux

https://warsug.info/viewtopic.php?t=15844
Post by JhG123 » Sat Nov 09, 2019 11:33 am
Guide for setting up POCSAG decoder on Linux
Tested on Ubuntu 18.04.3 and macOS 10.15 Catalina with an RTL820T2 SDR.

1.

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sudo apt update

2.

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sudo apt install rtl_sdr netcat sox gqrx

3. Clone this repository to the home folder

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git clone https://github.com/EliasOenal/multimon-ng.git

and cd into it
4. To build multimon-ng, follow these instructuctions, you will need make installed.

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mkdir build
cd build
cmake ..
make
sudo make install

5. Launch GQRX and go to Tools>Remote Control Settings and set the port to 7355, and add localhost to the allowed hosts list.
6. Attach your SDR and make sure GQRX is getting data, then tune to your intended paging frequency.
7. Click the UDP button, located near the bottom right of the GQRX window.
You'll want to set the Filter Width to about 11k and the mode to NFM, don't enable any noise blankers or AGC.
8. Launch the terminal and paste

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nc -l -u localhost 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 -

8. If all has worked correctly, once GQRX recieves a signal, which will appear in the waterfall as 2 streams of data, multimon-ng will start to decode them.

You may need to adjust some of the reciever settings to get a good signal, but it should work fine.

Last edited by JhG123 on Mon Jun 29, 2020 8:39 am, edited 1 time in total.