Ham Radio and linux - Decoding POCSAG pager transmissions with GQRX and multimon-ng
ฝัง
- เผยแพร่เมื่อ 9 ก.พ. 2025
- It's been awhile since I did a linux vid. So here you go.
Github page for multimon-ng:
github.com/Eli...
The command line I use to launch multimon:
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 -
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Hit me up on the echolink repeater down by my house: W9TE (Node: 519521)
After setting up my GQRX I was looking for more info about it. I came across this fascinating video about which I had no idea existed! I have learnt so much here, not least what the pipe symbol was really used for. Thank you so much for your time and effort. Good job...
Thanks for the tutorial - I was streaming stereo at 48khz to multimon, with no results. Your command line showed me the error of my ways.
The two opening tones sound like a doorbell. Like Ding-Dong --- page coming!
I have fat fingers so you are a saint putting the lines in the description!
Thanks Kevin, I have learnt lots from your ham radio linux vids, keep them coming :)
3rd time I am watching this video and it struck me that the method you are using to decode that rf data will work for my own private project so a big thank you keep it up
I think I've heard these transmissions while listening around but wasn't sure what they were... now I know! ;-) It's surprising that there's no encryption built in. Interesting stuff, thanks for the video.
Encryption will be used, at least in germany. It is called IDEA.
You are so professional and interesting, with great content! thanks
I was once watching text go by on PDW and they were in the guys hospital room trying to get a huge turd to go down the toilet. I LOL'ed
I didn't realize anyone still used pagers. Back in the day, I used to use mine for texting with friends. That was a real challenge! Oh, and you forgot to put that long command into the description, lol.
No, it's in there. Right after the github page link. Next line down.
It wasn't there when I posted it. All there was the first line and "SHOW LESS". Seriously, it wasn't there. It's there now though, yes.
What device or web browser were you using? I haven't made any changes since posting it originally. Maybe it's displayed differently on some browsers.
Using chrome. I looked at the page as soon as I got notification. Maybe the description hadn't updated when I checked it the first time. It's there now, so it's all good.
If you use Manjaro, All of these programs are available with a 1 click install in the AUR and official repositories
Are you running Linux? I ask because I am using a MAC. Will this run on MAC OS, just the way you instruct on this video? My SDR arrives in four days! I can’t wait to play with it. Thanks for any input or help.
Jim
Another great video!
Pager transmissions are still pretty active here in the UK too for medical services and remote monitoring of various hardware. Some are located down near the NOAA weather satellite frequencies (somewhere around 137 MHz) which can be a bit annoying. I know your focus was on linux here but it's probably worth mentioning the free software called PDW Paging Decoder that's available on the discriminator.nl website. It works well on windows machines - or so I hear ;0)
Is there a way to do this using windows? I have a raspberrypi 3b if not so will it work on that? I tried running SDRUno on the pi and you have to turn the bandwidth all the way down to 2Mbps or it overloads the rpi; processor is too slow. I can't remember why exactly but I use my SDRPlay on windows for a reason. Perhaps SDRUno is just too much for the rpi? Would other programs work better?
there are POCSAG de code programs for windows, do a Google search. I'm the pie, gqrx should work fine and the rest of these instructions as well.
Hello Kevin, I hope you are well. I run into a little problem. I have the official raspbian image from SDRplay for my raspberry pi. RSP1a is working with cubic and gqrx. I have also run the script from KM4ACK "build a pi" and installed a lot of Ham programs and the only one that I need is WJST-x and GridTracker since I want to run FT8 from the raspberry. I was wondering if I can set the FT8 freq in gqrx and press the UDP button to stream the audio over UDP port. The only problem is that WJST-x accepts only audio as input no options for UDP. Do you see any work-around on this issue? In windows, I run SDRUno and VB-Audio cable but since I want to be mobile with my raspberry... you get the idea. I have also bought a USB sound card for the raspberry and just connected a Jack to Jack jumper cable from the output to the mike without any success.
If any ideea comes to you please let me know.
Thank you,
Catalin Alb
DE1CTL
Install pulse audio volume control and use it to tell wsjt-x to use system monitor as its input. It will then process the audio coming from whatever program is generating it.
@@loughkb Thank you so much Kevin,
I did found something and it works well here is the link:
www.onetransistor.eu/2017/10/virtual-audio-cable-in-linux-ubuntu.html
basically I just ran:
pacmd load-module module-null-sink sink_name=Virtual_Sink sink_properties=device.description=Virtual_Sink
To make it permanent, open the configuration file (sudo nano /etc/pulse/default.pa) and add the following line:
load-module module-null-sink sink_name=Virtual_Sink sink_properties=device.description=Virtual_Sink
Since then the raspberry starts with the virtual_sink and everything is fine.
I have the raspberry pi with RSP1a, gqrx (official image from SDRplay and runned the script from KM4ACK).
I did run FT8 and have good results since the whole package is far away from the house and all the noise sources from inside.
I would like to know how I can receive the UDP stream locally. This way I can also listen to the broadcast stations.
If you are running FT8 please tell me. Yesterday I pointed my Vivladi antenna to West and received a lot of stations from USA on 20m from here in Germany.
Take care,
73! Catalin
DE1CTL
Another great video, dad. 73.
Thank you! Finally got it working. I do have one question though, regarding the background noise. Why is it at different frequencies the background noise levels drastically change?
Different noise sources, antenna choice, there's lots of variables.
@@loughkb cheers!
i have been doing this on and off for a while here in the uk. but most of it is just hospital data.. im on pc so i am using PDWv3.12 and an sdr dongle
Great tutorial and demo. Can this procedure (software & commands) apply to a raspberry pi?
Yes. it can be followed exactly and will work.
Great. I'll have to get a raspberry Pi so. I currently use PDW decoder (windows) which can send email notifications for particular IDs. Can multimon or an add on app do this?
It would be possible to do with bash scripting, but it would get fairly complex.
Someone has come up with this to forward decoded messages to email
www.rtl-sdr.com/forwarding-pager-messages-received-with-an-rtl-sdr-to-email/
very handy, thanks man!
Excellent
I have SDR Angel wich have the Pager decode In it,
Wow...that hospital needs to review their HIPAA policies and procedures. MRNs with names and diagnosis...not a good thing.
lol
Kinda like people who put their username and password on a piece of tape on the monitor of their computer.
After working in I.T. for 30 years, I can tell you that if you want to log in to a manager or executives computer... All you need to know is their spouse's name, kids names, and pets names. In rare cases, favorite sports team or player. Most of which can be harvested off their families facebook pages.
People don't take security seriously until they have to react to an invasion. It's the state of things.
Which is why pentesting and security audits are things. Simulates the kind of situation they might find themselves in if the bad security practices are kept up, and lets them learn from their mistakes without much risk of real harm. Wish people cared enough that they would take even 5 to 10 minutes to research good practices, and put them into their daily routine. I can't even imagine how many incidents wouldn't have happened in the first place if people just cared a little bit more.
May be a stupid question, but how did you determine the frequency for POCSAG transmissions local to your area?
Around 460MHz and up is a common commercial area for utility transmissions. I just looked around up there until I found some. They're easy to spot with the two close alternating carriers and the distinctive sound.
SO This is a Linux only thing?
There are programs to decode it on windows. multimon is probably cross compiled for the mac too. But this tutorial is using linux tools, it's in the title. "ham radio and linux". ;-)