Tutorial on Setting up OP25 for P25 Phase 2 Digital Voice Decoding

Most police departments is the USA have now upgraded or are in the process of upgrading their radio systems to P25 Phase 2 digital radio. The frequencies can easily be received with an RTL-SDR, but a decoder is required to be able to actually listen to the voice. Software like SDRTrunk and DSDPlus can decode P25 Phase 1, but at the moment the only software that is capable of decoding P25 Phase 1 AND 2 is a program called OP25. However, OP25 has a reputation of being fairly difficult to set up as it does not have a simple to use GUI, and requires Linux.

Over on John's Tech Blog, John has uploaded a very helpful step by step tutorial that should help with those trying to get OP25 to work. The tutorial assumes that you have Ubuntu 18.04 already installed, and then starts from downloading and installing OP25. The next steps involve setting up OP25 for the particular system in your area, which mostly involves just editing a spreadsheet to input frequency data from radioreference.com. John also mentions that he's been able to get OP25 running perfectly on a Raspberry Pi 3 B+ as well, with less than 40% CPU usage.

OP25 Running
OP25 Running

In the video below John reviews some of the steps, and shows OP25 running and decoding voice.

OP25 Tracking 2 Control Channels

30 comments

  1. gapa17815

    I am in a medium sized county in central PA, they went P25 full encryption about 2 months ago. Fire and EMS still unencrypted for now, all Police are on 1 channel and the officers i have talked to HATE IT!

  2. David Anthony

    The trick to getting this working is to use the ” keys to fine tune the spectrum. You may also need to use the ‘.’ and ‘,’ for more precise adjustments.

  3. DallasTechie

    Dallas Texas has remained using analog but with DCS encoding. Most suburban cities have switched to P25 phase 2 with a lot of them using encryption. Irving, Carrollton, Addison and Farmers Branch have switched to P25 Phase 2 with Encryption for the whole city including public works, streets, animal control etc…. Sort of scary when the whole city switches to full encrypted communications. Makes you wonder what they are hiding.

    • KC5UZD

      Agreed. Johnson county (Burleson, Joshua, etc) has joined the party. Sure wish SDR# had Windows decoding software for Phase II.

    • michael pontisso

      This will make every person not in government an enemy of the state only.And no accountability at all. They are the standing army we were warned about. And are the modern day Red coats .

    • Kyle Martin

      I can definitely say farmers branch is known for profiling. I grew up there,
      Back in the late 80s before they switched to trunking I used to monitor them
      the police would use vhf 154.9500 as channel 3 as the talk channel. I would hear them say stuff like..he doesn’t look like he belongs here .. let’s see if we can get P.C to stop him

  4. Techie

    Dallas Texas has remained using analog but with DCS encoding. Most suburban cities have switched to P25 phase 2 with a lot of them using encryption. Irving, Carrollton, Addison and Farmers Branch have switched to P25 Phase 2 with Encryption for the whole city including public works, streets, animal control etc…. Sort of scary when the whole city switches to full encrypted communications. Makes you wonder what they are hiding.

  5. Craig

    I got it working after hours and hours of trial and error. The decoding is near perfect. Quite an involved setup but we’ll worth the time. Next is to make it work with an RPi. I also have it streaming for my personal use using icecast2, Pulse and Darkice.

    • Rob Dale

      With 15,000 local police agencies in the US it is going to need to be a longer list before we get to “most” 😉

  6. Rob Dale

    Small error correction off the top… Most police departments are analog and are not changing anytime soon. A good number are P25 Phase I. Some are Phase 2. More will be shifting up with time, but clearly P25 Phase II is in the minority now.

    • Ron

      Wrong! Lately most large police departments either just changed to digital or planning on it. Maybe the small communities which don’t have the money to upgrade are using analog, but I have seen many medium to large cities move to digital, and mostly P25 Phase II. That is why I don’t have a trunker monitor anymore, the last 4 places I have moved to are all P25 Phase II now. At least that’s how it is in the US.

      • Rob Dale

        Here in the US, MOST POLICE DEPARTMENTS (using the phrase from the opening line of this post) are NOT on Phase 2. Most are not even on P25. Some larger departments are, but MOST are not.

        Let’s try the largest. NYPD: Analog. Chicago PD: Analog. LAPD: Analog. Detroit PD: P25 Phase I – might go Phase II in the next decade.

        • AD5NL

          Digital is definitely rolling out though. I’m in rural-ish Maury County TN and I believe both Spring Hill and Columbia (the two largrst cities in the county with about pop 40,000) are on digital now for the police. The County Sheriff and Fire/EMS are migrating but still have an analog simulcast.

          Austin TX was on Phase I P25 when I left about six months ago. Ironically it might be harder to move larger systems than smaller ones.

    • maus92

      Moto SmartZone and Harris EDACS are EOL. They will be replaced by TDMA (P25P2 systems) because they can theoretically double the capacity of the system.

    • Brian

      2021 most state public safety departments including my state are switching to a new nationwide p 25 phase 2 lmdr system. Which allows access to the new win link cellular phone networks hybrid radio system.

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