Trunking Communications Monitoring - Part 2
by TELEgozilla
By now, some of you (maybe) started listening in on the airwaves and found a great many interesting things. This article is a follow-up, offering some tips and more in-sight as well as various data sites for you to check out.
When you're monitoring a trunked radio system, your tracker will begin displaying group identification numbers - i.e., talkgroups. Trunked radio systems are organized vis-à-vis radio groupings. With your tracker, you'll be able to tune in (or out) those groups you want to focus in on.
I found this to be most interesting when listening in on state police talkgroups, as I can determine who is in charge and who is doing the patrolling - and monitor accordingly.
There are other tools and informational points to consider tapping into. A good approach to consider is that of PC/scan kits. You can get ahold of a trunk tracker (such as the Bearcat/Uniden BC895XLT), plug into a PC, and let it do all the work for you.
The PC will log and note the times and groups scanned for your future reference later on. Along the lines of scanning, you should consider getting your hands on a digital receiver. Mobile Data Terminals (MDT), DTMF, CTCSS, along with a host of other goodies fly through the air all around us. Having a digital receiver can decode those signals. Some of those signals can be most interesting - and remember, it's not just the police who use digital transmitters.
Some models to consider are the Optocom (sales@optoelectronics.com) as well as the OptoTrakker.
As of this writing, there are various types of trunked radio systems. Some trackers can only handle the 800 MHz range, but there are also 400, 500, and 900 (and the soon to be announced 700, if it isn't out already) MHz trunked radio systems.
The OptoTrakker can monitor all those trunked systems (sweet!) while also handling digital signals (all for about $300). So you can go to work, drink, or generally let your PC/scanner do the work and it'll automatically log where and what's going on. You'll still have to do listening, but this approach saves you a lot of time and trouble (unless you're like me and enjoy the thrill of the hunt).
Speaking of hunting, if you're not sure about what's being transmitted around you, then consider getting a frequency counter.
Frequency counters are hand-held devices that behave like a regular receiver, except that you can't talk through them; they simple scan a wide frequency range (usually about 10 MHz to 2 GHz) and, depending upon the type of counter, will capture and store the active frequencies in your area - if not decode the digital signals being sent on the airwaves. Take a walk on the wild side around your various target areas. Shopping malls, stores, utilities, and whatnot all use some type of carrier wave. The trick is to find them, catalog them, study, and then, well, learn.
Your standard approach will be (regardless of whether you're tracking trunked systems or not):
- Go out with a counter and get the frequencies.
- Set up your tracker/PC scanner.
- Log the activity.
- Go back and listen in.
- Look up your frequencies to see who's what.
When scanning/tracking, you may encounter a system that's somewhat protected (besides being encrypted) against scanning. Some system operators will program a "tail," that is, a transmission delay that creates a hang time for the scanner.
In effect, the user stops talking, and you'll (usually) hear a series of one to three second beeps. What this does is that the channel/repeater which just finished broadcasting a voice or data transmission remains open long enough to lock up your scanner - thus preventing your scanner from scanning the other channels where the conversation (or conversations) may have continued.
Bad news; there's really not much you can do about this except to push the "search" button and keep on going. Fortunately, referring back to what I said earlier about hierarchical systems and how those with brains and initiative are usually not appointed to positions requiring either, you shouldn't encounter this development all that often.
There are various sites and sources of information to consider. Check up on some tips and other trackers' experiences:
Here's a place to check out equipment pricing (no, I don't own any shares in the company and there are plenty of other vendors to check out):
After monitoring, when you do get frequencies, here's one place to go and find out whose they are. Similar information can also be found on CD-ROMs or frequency books (I prefer CD-ROMs as keyword or number searches are done far more quickly):
Want to know where there are trunking systems? Here's a spot to check out: Trunked Radio Systems User's Page
There are a wide variety of excellent access sources that I found to be most useful - books, magazines and various CD-ROMs. Reading is wonderful. I also highly recommend that you get a copy of the December 1998 issue of Monitoring Times, and read the article, "Challenges in IDing Trunked Radio Systems." Great overview!
Well, I hope you found this article to be somewhat useful. Wired is cool, but wireless is also definitely hip.
With today's growing reliance on multi-frequency systems, being there on the air is cutting edge. With DTMF decoding, trunk trackers, and PC scans - along with handy reference books and databases, the airwaves are there for the taking!