Ok I’ve been on a roll playing with OP25 and Raspberry Pi and one thing I can tell you is that the onboard audio from the bcm2835 chip is somewhat inadequate. Oh, it works but you’re going to need a powered speaker or really efficient headphones, and even then it is a bit light.
What to do?
Add a USB Digital to Analog converter (DAC). Depicted here is a HiFiMeDIY USB DAC. This is a tad bit expensive for this project but I have like 4 of these things laying around the house. They are ridiculously good. If you like music slap one of these bad boys on your laptop in the hotel room and the quality of your music will improve ten fold.
That’s not what we’re doing here though.
There are a LOT of USB DAC’s out there and some cost just a few dollars. HiFiMeDIY makes some cheaper ones as well that are way more than enough for improving your OP25 sound.
The Phat DAC costs $15 but you’ll have to solder header pins on yourself. That may be the cheapest, and best route. It has the form factor for the Raspberry Pi Zero but it works on all the Pi’s.
In my last part I set the Pi up to stream to Broadcastify. In this one we are just going to pump audio out through the headphone jack.
I’m doing this with an old generic black RTL-SDR and it works and it works fine but it is kind of susceptible to heat and cold and the ppm correction drifts a bit. I really recommend getting a v3 RTL-SDR or a NESDR Smart as they seem more stable. At any rate it doesn’t matter, you’ll just have to deal with the drift if you have any.
My assumption here is that you have Raspbian installed on at least a Pi 3. I haven’t tried it on a lesser Pi but I had it on a Pi 3 B + and then I found a couple Pi 3 B’s laying around and figured I’d reclaim my B+ for another project on another day. OP25 runs fine on the Pi 3.
So I finally figured out OP25 and I have this brand new Raspberry Pi 3 B + laying around doing nothing. In this segment we’ll install OP25 on Raspberry Pi and then take our police scanner feed and send it to the internet on Broadcastify.
As someone pointed out to me yesterday, “There’s an app for that” they are indeed correct. You can get Police Scanner Apps for IOS and Android. Guess where the feeds in those apps comes from? If you said Broadcastify you’d be correct. So if no one is feeding your municipality then there will be no feed in the app. We will be that feed.
So the assumption is that you have a Pi with Raspbian installed and you kind of know how to use it.
OP25 is a program that decodes P25 Phase 1 and Phase 2 digital radio. Some municipal areas are upgrading to P25 Phase 2 so almost gone are the days that you can track them with a police scanner since P25 is a Trunked Radio system and not just a lone frequency to monitor. The only things that do Phase 2 are hardware scanners and hardware radios and OP25 for software radios. Bear in mind Phase 2 could be encrypted and nothing you can do will decode it.
OP25 is HARD. I’m a geek and I messed with it on and off for a year or more and it whipped me more than once. Now that I have it working I find that it is REMARKABLY easy and I’m mad at all the geeks out there who never made a simple tutorial. There are tutorials out there, some good but everybody leaves out the good stuff or the stuff they took for granted.
So, you are a government employee AND a Linux geek. Join the club. It is possible to use your smart card to access DOD CAC Card enabled sites. A must do project for the Linux geek in you.
I’m doing this with an IOGEAR GSR202 and it will work with a lot of other CAC Card readers as well. Also I’m using Ubuntu 18.04
First of all the information is taken from this excellent website. While almost perfect there are a few minor issues that could foul a fella up. I seek to clarify those here.
First lets download the Certs for your browser. They also come from the page I have linked above (MilitaryCAC.com). Download here. Hold tight. We’ll get back to them.
First you need to download the latest Raspberry Pi Raspbian OS from here. Get whichever version you want but I like to get the desktop version so I can VNC into it as it makes it easier.
If you have never done this connect your Raspberry Pi to a monitor, keyboard and mouse. If you are an old salt with Linux then just run headless and SSH into your Pi.
Once you download that file UNZIP IT. UNZIP IT. The file will end with an extension of .img
Do NOT try to burn the zip file to your SD card. UNZIP IT AND GET THE .IMG FILE.
This is one of my favorite subjects. Repurposing an older computer and using it when there is no available internet connection. If you have internet that is a big plus and you can and should use it but computers are still pretty useful with no network with the addition of a couple of pieces of inexpensive hardware.
What can a computer do that isn’t hooked to the internet? Quite a lot actually. Here’s a few things you can do:
- Watch digital over the air television
- Listen to FM or AM radio
- Listen to Shortwave Radio
- Listen to Amateur Radio
- Listen to emergency service transmissions such as police, fire, weather, etc.
- Decode NOAA Weather Satellite Images
- Detect Aircraft Overhead
- Decode Digital Transmissions that are unencrypted
DSD+ is a popular Windows digital decoding program that handles various digital protocols. I’m going to install and use it with WINE on Ununtu 18.04. The example I’ll show here today is a digital trunking control channel that the local Emergency Services uses. Without DSD+ the signal will sound like this:
I set Screen Sharing up on Ubuntu 18.04 but then found out none of my clients could connect to it. After a little digging I found that in order to use VNC Viewer (or other software) from another computer that I had to disable encryption. Yeah, not ideal but I need it to work.
First go to Settings and then “Sharing”. Make sure to turn the Slider in the upper right hand corner to the ON position.