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:

        /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

5 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.

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