Update on P25 scanner — new version, and new installation instructions

Since I posted my original articles on configuring the Gnuradio-based op25 P25 trunking scanner, there’s been a lot of progress in the code. In particular, there is a new fork that changes the program to a command-line version, which saves a lot of CPU resources and also offers added features. The new version will run nicely on a Raspberry Pi 3, and probably on an RPi 2 as well. Following are instructions to install it from scratch on the PI.

Download the “raspian-stretch” image from raspberrypi.org and copy the image to an 8GB SD card. There’s a very nice free tool to do that called Etcher. Install the card in your Raspberry Pi, and connect the Pi to the internet.

Open a terminal window to run all the following steps.

First, update the system and add the “sources” repository:


  • sudo nano /etc/apt/sources.list and remove the “#” from the beginning of the line that includes “deb-src”.

  • sudo apt-get update

  • sudo apt-get dist-upgrade


    • Reboot the system before the next step.

      Now, download and build the op25 code:


      • cd /home/pi

      • git clone https://github.com/boatbod/op25.git

      • cd op25

      • ./install.sh

      It will take a while to download and install all the packages, and then compile the op25 code. But when the installation finishes, you should be all set to go. But there are a couple of additional things that I do on my system to make life a little easier:


      • The program and config files are buried several layers down in the op25 directory. I make a symbolic link called “scanner” to that directory:

        ln -s /home/pi/op25/op25/gr-op25_repeater/apps /home/pi/scanner

      • The program command line requires a whole bunch of parameters that are hard to type (and to remember!). I create a shell script to start the program:

        #!/bin/bash
        /home/pi/scanner/rx.py --args 'rtl' --gains 'lna:35' -S 250000 -f 853.6e6 \
        -g 100 -q -1 -o 50000 -T /home/pi/scanner/trunk.tsv --udp-player -v 5 2>stderr.2


8 thoughts on “Update on P25 scanner — new version, and new installation instructions

  1. When I use SDR Sharp with my dongle to use as a regular scanner, I use the default sound card on my laptop and I hear everything I want. But when I want to use DSD to decode P25 per the instructions I change the input on my sound card to VB Cable and the output on SDR Sharp to VB Cable, I hear nothing. Is that a normal thing. Will I hear something through my computer speakers when the dongle picks up and decodes a channel with digital P25? Is it normal to not hear anything at all on my speakers when the sound settings are like so? Is that the whole purpose of VAC or VB Cable? FYI, I am using XP. Any insight would be a big help. Thanks!

    1. Hi — I’m sorry, but the questions you’re asking are related to a completely different system than the one I described here. I’m afraid I don’t know anything about using SDR Sharp to decode P25.

  2. Hi. I am a complete noob. I managed to successfully follow the instructions to install this new version. Everything appears to have loaded up correctly. But now I am not getting how to do the final 2 things, the ‘scanner’ link and the ‘shell thing’, you recommend has got me stumped and believe me i have tried albeit unsuccessfully everything I can thin of.. I am very interested in working on many SDR projects among this one. Thanks in advance for the amazing work that you have done to simplify this often difficult and mind bending subject of configuring all this SDR programming into a single package. Frankly I think this will be the only way I will be able to do it for now until my current knowledge base has developed to a level where I actually feel comfortable with creating and modifying codes, etc. I am very curious to see this up and running, but until I am able to execute the program (and complete the last 2 tasks) I wont know for sure if this is even working or not.
    Additionally, i have worked this project so far on rpi3b with raspian buster full.

    I think its just a bit of help needed at the finish line! Hopefully, but I can not even figure out how to execute what I have so far.

    Please help me in the simplest terms you can. Rpi, Linux, Ubuntu, etc I only started to learn about a few weeks ago.

    Thanks in advance and I hope you are able to understand my problem and respond appropriately.

    Sincerely,

    Kevin Bedore

  3. The install went fairly well as far as I can tell. Being very new to Pi, Linux and all, I am a NOOB, big time. I won’t truly know if I have successfully performed a good install, because I did not understand how to do the last 2 points recommended shown below, nor do I know how to execute the program.

    Any help you can provide in the simplest of terms, would be greatly appreciated.

    Thanks in advance.

    Kevin

    _______________________________________________________________________________

    “”The program and config files are buried several layers down in the op25 directory. I make a symbolic link called “scanner” to that directory:

    ln -s /home/pi/op25/op25/gr-op25_repeater/apps /home/pi/scanner

    The program command line requires a whole bunch of parameters that are hard to type (and to remember!). I create a shell script to start the program:

    #!/bin/bash
    /home/pi/scanner/rx.py –args ‘rtl’ –gains ‘lna:35’ -S 250000 -f 853.6e6 \
    -g 100 -q -1 -o 50000 -T /home/pi/scanner/trunk.tsv –udp-player -v 5 2>stderr.2″”

    1. Hi Kevin —

      Sorry it’s taken me so long to reply to your posts; I hope that by now you’ve figured out what you need to do. But just in case, these are both commands that you issue from the terminal window command line. The first one, “ln -s” makes a link to a file from one place to another. So, the command I gave just makes the “scanner” program available in the user’s home directory, so you don’t have to type the long path to where it really is.

      The second bit of stuff is meant to be typed into a text file using an editor program, to create what’s called a bash script. When you run the script it will execute the commands in the script. So, use an editor to create a file, copy those commands into it, then save the file. In order to be able to run the file, you need to either preface it with “bash “, or make it “executable” by issuing the command “chmod a+x “. Then you can run the file just by entering it on the command line.

      I hope this helps a bit. Unfortunately, working with the guts of the op25 software requires you to use the Linux command line, so it will probably pay off to find some tutorials on that.

      John

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