Digital Trunking Police Scanner

police scannerWhen I was a kid, I used to spend hours listening to my 20-channel Radio Shack police scanner, often times waking up to an alert or static that broke the squelch. Over the course of five or so years, all the police and fire departments started moving to the 800 Mhz band for which my scanner could not receive and I slowly lost interest. Not having the money to buy a new scanner, I found other fun things to do with my spare time.

Flash forward 30 years and once again my curiosity has funneled me into an old, but new hobby; scanning. But it isn’t nearly as simple as it used to be and I found myself seriously studying how the newer technologies work. I found that Police, EMS, Fire, Search and Rescue, and other services in Colorado use DTRS (Digital Trunked Radio System). What the heck is that? Well, it’s complicated. In simple terms, the radio transmitters and receivers all change frequencies very quickly and you need to have a scanner that can decode the data and follow the frequency hopping.

It doesn’t stop there. There are new terms I had to get familiar with. Things like System, Site, Group, Target Group, and alternate channels to name a few. For example, with DTRS you need to find a tower usually 850 Mhz range (System), locate the control channel frequency (Site), then scan the control channel for Target Groups which are digitally encoded “channels” that contain the voice data which hops around the voice frequencies. Once your scanner locks onto a group, it too will frequency hop so you can hear the conversation.

Think of it this way: You scan for police, EMS and Fire within the control frequency.

It took a few days to get a handle on it, and it’s actually not that complicated. One just needs to reprogram their brain from the old school concept that city police use one frequency and fire use a different frequency. Ironically, they all use the same frequencies, but not at the same time. The control channel (tower) coordinates the digital transmission much like an air traffic controller coordinates airplanes. This allows hundreds of groups to use the same set of frequencies and never transmit over one another.

So, what scanner can decode the digital trunking system? Well, unfortunately, there aren’t that many and the ones that can are rather expensive. I chose the Uniden Bearcat bcd996XT. It’s the base station model, although it is small enough and has all the connections to mount in a vehicle. It’s just not hand-held, but that didn’t concern me. The unit feels very sturdy. One of my pet peeves are crappy buttons, and fortunately the 996XT has solid buttons. Although I haven’t tried this yet, you can hook up a GPS to the scanner and have it turn on and off different systems depending on your location. That may be pretty cool for the serious scanner enthusiast, but not me. I did read reviews that the digital decoding on the Uniden 996XT wasn’t as good as some of the other units out there, but it sounds perfectly clear to me. Far more clear than the old old analog scanners. And if you are interested, the scanner can receive AM and FM signals so you can still listen to the older technologies if you want to. It just so happens that Colorado almost exclusively uses DTRS in the 850 Mhz spectrum.

I haven’t had a single issue with the scanner yet and have somewhere around 200 target groups programed. The manual sucks though, big time. It’s virtually useless, so be prepared to go online for answers to your questions. A place to start is RadioReference.com

Please note, very few cities or states use DTRS and therefore you don’t need a fancy scanner like the 996xt. There are other less expensive units that will work just fine in those areas, but if you live in Colorado, you will need a scanner capable of decoding digital trunked signals.

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