StarComm21 help

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Premium Subscriber
May 15, 2008
Champaign, IL
Good morning. I apologize if these questions have been asked before and/or if I am posting this in the wrong forum.

I'm not new to scanners by any means, I've been using them since the early 80's, back in the day when you had to purchase a crystal for each frequency you wanted to listen to and if you changed your mind you ended up with a collection of spare crystals. I know there are some of you asking crystals....what? I have worked in Fire/EMS field since that time and have used the scanners to keep up on what was going on at work and to just basically keep informed.

I never had to worry about trunking or any of that until the last year or so. Many of our local agencies switched over to digital trunking so began the learning curve. The last 2 of my scanners I had purchased were trunking scanners but seeing how none of the agencies I wanted to listen to used trunking systems I never bothered to learn about trunking systems or how to use this capability. Then after learning our local agencies switched to trunking I began the learning process only to find out my scanners were useless because they didn't do the digital trunking, so then I had to purchase a new scanner...not that I complained too much except for the price :(

I purchased a BCD 996T and it seems to work fairly well. I use the ProScan software to program it and listen to the scanner remotely, but I currently have the scanner in the car. I love the fact I can use a gps receiver to lock in and lock out sites as I travel, thus this brings me to my questions.

When I am traveling throughout the state of IL I like to listen to various agencies while I travel, but probably the most traffic is the State Police who uses StarComm21, but I have the other agencies who use StarComm21 as well programmed in.

Can someone explain to me how this trunking system works...basically. I know how it works for my local agencies...all of the computer assigning a frequency to the person when the key up etc. I'm more curious as to why traffic from Champaign isn't heard in Cook County etc. Also, what happens when one of the troopers goes out of his/her district do they have to switch something or what. Prior to trunking, if we went to another area we usually had to switch to that areas frequencies to communicate with them, but I'm not sure how this works with trunking.

I have all of the StarComm21 sites/frequencies programmed into my scanner, along with all of the ISP talkgroups. While traveling here in Champaign County I hear traffic identified on the following talkgroups, Dist 10, Dist 21, Dist 6.

Now the BCD 996T has limitations of so many talkgroups per system and so many sites per system, etc., so I have had to program in 4 different systems for the StarComm21 trunking system to get all of the ISP and the other agencies I want to listen to that use the StarComm21 system.

Any help and explanation would be greatly appreciated.



Dec 14, 2001
Far NW Valley
StarCom21 is an P25 networked trunking system. Every radio has an individual ID that is sent with every transmission. When a radio assigned to Talkgroup (TG) 9000 (for example) transmits, the system sends all the other radios set to TG 9000 to what ever frequency is available for use.

SC21 has hundreds of radio towers ("Sites"), and each tower has anywhere up to a dozen or so channels assigned to it. If there is a radio set to TG 9000 at Site #112, then one of the channels assigned to Site 112 transmits the voice message that our user speaks and any other radios tuned to TG 9000 on and connected to Site 112 will automatically be tuned to the frequency selected by the system controller.

If another radio is tuned to TG 9000 but is connected to Site 301, then the controller will assign an available channel at Site 301 to send out the message. All these activities take place in a fraction of a second.

All radios on the system Affiliate with a local tower, and as the user moves it may change to different towers much the same way a cell phone does.

The various TG's are set up to work in certian areas. For example, if Mayberry has purchased access to the system they can choose what level of service they want. For $53 per moth per radio they can have TG's that work anywhere in the State. For less money they can have TG's that work only in a certain area, say a couple different counties. For even less money they would get access only to a small area, maybe just 1 or 2 Sites.

If a system radio is set to a talkgroup in your area then the local site will rebroadcast the conversation and you can hear it on your scanner. If there are no system radios in your area on that TG then you won't hear it.

While most of the traffic you hear is local to the area occasionally troopers from different areas of the state may travel near you, maybe they are going to a meeting or training session. Since they like to hear thier local district they often leave the radio tuned to their home district, so occasionally we hear southern IL districts in the Chicago area.
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