Creating a Pager using a Raspberry Pi and RTL-SDR to send alerts via Email

Posted by Jack Riley on 2018-09-04 11:34:18.

As part of a university assessment, I was tasked to develop a system incorporating the Raspberry Pi. Although I had used Linux frequently, this was the first time I had owned such a portable and versatile computer, and it got me thinking about fun or creative projects using the Raspberry Pi.

I have been tinkering with SDR and radio technology since around 2015, when I first obtained an RTL-SDR. I have since upgraded to a SDRPlay RSP1 for most uses, however I still carry my RTL-SDR with me wherever I go, as it takes up little space in my bag. 

Until this project I had exclusively used Windows for any SDR project. Knowing that the Pi has good support for the RTL-SDR and there were a number of programs I had wanted to use with an SDR, I thought it would be a fantastic opportunity to explore some new software, while keeping my project interesting and informative.

I decided to choose POCSAG pager decoding for a couple of reasons. These were:

Using rtl_fm and Multimon_ng, along with a custom Python script, I was able to receive, decode and process POCSAG transmissions. The received messages were analysed to determine their recipient, and if matched a list given to the Python script, it would generate an email to a specified address. The result of this was a pager receiver, that instead of alerting a user of a message using beepers and vibrating motors, sent them an email. I suppose it’s linking the old technology with its successors!

I have uploaded a copy of the script that I made along with some supporting documentation on the development of the project. The Python script does work but has significant room for improvement. Some ideas I had were to extend functionality to protocols other than POCSAG, or to send the processed messages to a web interface for searching history, etc. You are welcome to use or extend the code for this project. If you improve the script and are willing to share it, email me and I will add it to this post and credit you.

I have also made a video on this project, which can be viewed below.

17016-RaspPi POCSAG RTL-SDR Pager.pdf