Pager message sniffing with RPi and SDR

rpi-pager-message-sniffing

The 1990’s called, they want you to use modern technology to listen in on your friends’ pager messages. Seriously, how many people are still using pagers these days? We guess you can find out by building your own Software-Define Radio pager message decoder.

[Sonny_Jim] bought an RTL2832 based USB dongle to listen in on ADS-B airplane communications only to find out the hardware wasn’t capable of communicating in that bandwidth range. So he set out to find a project the hardware was suited for and ended up exploring the POCSAG protocol used by paging devices. It turns out it’s not just used for person-to-person communications. There are still many automated systems that use the technology.

Setting things up is not all that hard. Reading the comments on the project log show some folks are having dependency issues, but these sound rather banal and will be a good chance for you to brush up on your Linux-fu. Once all the packages are installed you’re simply working with text which can be displayed in a myriad of ways. [Sonny] set up a text files on the Pi’s webserver so that he can check out the latest captures from a smartphone.

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33 thoughts on “Pager message sniffing with RPi and SDR

  1. Even when smartphones were coming on the scene, my boss (laboratory supervisor) still used a pager (not sure who typically paged him). I believe many doctors still use them for priority pages from their hospitals and then they can use a cellphone to call for more info.

    1. In hospitals there are areas where they don’t want transmitters, so then a pager is good.

      And people that hate the constant tracking by the government and google and such are also helped by it, since it receives only so they can’t track your movements.

      And then there are those who don’t want to have to constantly answer calls from annoying people I guess.

  2. The Mayo Clinic still uses pagers, hundreds, if not thousands, to contact employees over their wide ranging campus.

  3. So… he compiled one of the tools which comes with the gnuradio suite and ran it on a raspberry pi. Totally a fun and amusing thing to do, but it’s not a very impressive achievement. One of the tools that comes in the gnuradio suite allows you to decode an entire 1MHz band of pager data, and my old desktop can’t handle that much data. If he got THAT working on the pi board, now that WOULD be impressive.

  4. Restaurants use something like a pager to notify you that your table is ready. I don’t know what the underlying technology is, though.

  5. All hospital doctors carry a pager or two. Call them bleeps don’t think they work in the same way sim card pagers work.

    Sure some hospitals must be moving away from the pager system but I suspect the “crash team” who respond to emergencies will use them for quiet a while.

  6. I work in a hospital servicing the medical equipment, and we use pagers all the time, especially for emergency calls.

    Cell phones still do not have consistent reception everywhere, but the only place my pager won’t work is on the subway to and from work.

    1. That’s exactly why so many are still in use. The paging signal is very low bandwidth, so it can operate at much lower signal levels.
      Back in the day, I was amazed at the places where my pager would work.

  7. Also still used by the volunteer fire services to contact their personnel without using a loud and obnoxious siren.

    1. I was surprised when I heard this from other volunteer firefighters. I wish we would have had POCSAG or FLEX type pagers that could have received the address of the call or other pertinent information. All we had were Motorola Minitor pagers which were a radio receiver with tone-activated squelch. The dispatcher would transmit a two-tone signal and when our pager heard those two sequential tones, the squelch would open so you could hear the dispatcher talking.

      Not real handy when you received a call driving down the road and couldn’t write down the address you needed to go to. Later models at least had an audio recording feature so you could play back the first 60 seconds of audio after the tone to hear the address again.

  8. Reminds me of the late 90s/early 2000s when I messed around with decoding POCSAG with a wideband scanner and a computer sound card. That was back when a pager was $10/month with free hardware versus $300 brick cellphones with $150/month plans, so most people in my area still had pagers.

    Even the local law enforcement agencies only recently moved away from alpha pagers to receiving dispatch data via their MDTs (mobile data terminals).

  9. I wish I still had a pager. The list of excuses about why you were not *immediately* contactable by the GF is almost limitless. Add the fact that the phone was “forgotten” at home and that’s all you need.

    1. Encryption for what reason? Seems a waste of effort/money and a bit suspicious, especially since the dutch cops are becoming more and more ‘americanized’.

  10. I did something similar to this, and I was very surprised to see unencrypted patient names, room numbers, and other personally identifiable information being sent.

  11. Pretty much every department in my hospital uses pagers because cell service is so spotty when dealing with protective walls or working in the sub-basement. Our building automation system also pages out warnings for alarm points so the trades can get to the problem right away. You don’t usually see it on Grey’s Anatomy or House, but there are other people who work in hospitals besides doctors and nurses.

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