It was the best of decoders, it was the worst of decoders……… As you can tell I’m quite the literate bastard and highly up to speed on my Dickens.
I love digital signal decoding as it is almost something that you seemingly aren’t supposed to do, hence the attraction of it all. There are several hunks of software that can decode digital signals and each one has it’s strength and weaknesses. The ones I have dabbled around with are:
There are certainly others, not to mention maybe the most powerful one (but by far the one that requires the most geek foo) is GNURadio.
One of my favorite programs for decoding digital audio is DSDPlus. I’ve been using it a couple of years to dissect and decode SINGLE digital signals. Like for instance if I’m in the airport or airport hotel I can listen to DMR radio where the baggage handlers are talking to each other, or the mall cops are planning how to be real cops. Or you can hear the hotel staff on their radios which is sometimes really fun.
BUT…….DSDPlus also follows Digital Trunked Radio. That is where there is a Control Channel which is monitored and then the calls are “trunked” to available frequencies allowing for more users to use the system without confusion. Also users can be placed into Talk Groups which keeps down the confusion even more. Entire cities can use one radio system to control municipal services such as Police, Fire, EMS, Public Works, Events, etc.
Hurricane Florence coming! You’ve all seen weather radios and you’ve all seen they generally cost $50 or more. On a good day you can find one for $35 or so.
The goal is to receive NOAA which transmits on the following 7 frequencies. There will be one or two specific to your area. The frequencies below are in MegaHertz (MHz).
So I bought the Uniden SDS100 hardware scanner, and I love it. But it cost $700, and then I added DMR decoding for $60, and NXDN decoding for $50. So I’m into this in a big way. The SDS100 is POWERFUL. It is not a toy by any stretch of the imagination. It comes with free control software called Sentinel (yeah the download is hard to find on that page). Sentinel is adequate for managing favorites and reading and writing to the scanner and it is all you NEED.
However I stumbled across this hunk of software called Proscan which looked interesting but it also costs $50. Where does the cost with this scanner end? Well, like most programs Proscan has a 30 day trial version so I gave it a shot. After playing with it for like an hour I knew it was worth the cost so I bought it. It does NOT disappoint.
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.
We all know what the Internet is but what in the world is the Othernet? (It used to be called Outernet). The Othernet is unofficially dubbed “The Internet in Space” or “The Encyclopedia in Space” and it’s mission is to provide internet type information to the poor or to areas on earth which don’t have active internet.
I kind of view it as a back up to the internet and one more source of information in a SHTF scenario. When the grid goes down as long as you have an othernet receiver and a generator or some batteries and a laptop the satellite in space will probably still be working fine.
The project is housed here. Before you jump into the Othernet fire for the first time, know this. When you buy Othernet hardware, that’s all you get. No manual, no instructions. Nothing. That being said one of the users over there made an amazing guide to setting up the Othernet.
If you start digging into this guy a bit he’s highly credentialed and you can better believe this hobbyist believes everything he has to say in this paper. So it’s really all good.
Do you want to listen to your Shortwave receiver at work? Do you camp? Do you travel and can’t carry a lot of gear with you? If you did travel you can’t carry the gear with you to get the performance you get at home. Here’s a way to access your short wave antenna via an RTL-SDR device. You can’t really access your shortwave RADIO but you can get at your antenna.
You need an RTL-SDR device.
$30 gets you basically every radio frequency that you can imagine and there is no shortage of geeks out there to write software to listen to or decode or make use of all those radio signals. One really cool thing you can do is to set up a server which you can connect to from anywhere.