Radio system Talkgroups

[APX8000user133]

So I know that they exist because obviously we use them, but coming from someone who doesnt know much about it, im curious, those who upload stuff to the database, how do y'all find that information? Is it just frequency searching and when a transmission comes through it gets written down along with the CC or VC or radio ID's. I've always wanted to know how it happens.

 

[nd5y]

In the US for non-federal industrial/business and public safety (state/local government) users if you find a frequency and know the approximate location you can look up licensees on the FCC web site or here on RR. You need to know the exact assigned frequency to do that and sometimes scanners or SDRs don't display the correct frequency.

Some conventional (non-trunked) systems have multiple channels for different locations.
Some trunked systems have mutiple sites for different locations.

For analog all you have is a frequency and PL or DCS.

For conventional digital instead of PL and DCS, depending on the system type, you have NAC, Color Code or RAN, usually radio ID and maybe talkgroup ID.
For trunked systems you always have talkgroup ID and radio ID.
On some systems in some cases you can have radio IDs of "0" or empty/blank.

To identify channel usage you need to be able to listen carefully, notice things and take notes.
It helps if you know prowords, codes and signals used in your state/regional/local area or service/industry.
Notice channel/talkgroup names and IDs and unit IDs (voice) used.
Recognize individual users/voices (can be hard on some digital systems).
Notice radio IDs on digital systems.
Notice patterns like which users/ID on which talkgroups/channels.
Notice patterns like radio ID and talkgroup ID numbering and gaps in numbering.

Sometimes state/local/regional government web sites can have useful information.

Other people should have good tips or ideas that I left out or forgot.

 

[Echo4Thirty]

So I know that they exist because obviously we use them, but coming from someone who doesnt know much about it, im curious, those who upload stuff to the database, how do y'all find that information? Is it just frequency searching and when a transmission comes through it gets written down along with the CC or VC or radio ID's. I've always wanted to know how it happens.

Sometimes folks from the radio shop will post the talkgroups to the database.

 

[Project25_MASTR]

Sometimes folks from the radio shop will post the talkgroups to the database.

I don't know if a municipal shop would do that...certainly had a couple of MRs techs do that. In fact, someone just pushed some talkgroup IDs and aliases on here from one of my counties that you'd have to know either from having a codeplug or being in one of the agencies to define.

 

[Echo4Thirty]

When I was managing a former system that was barely on the air, our TGs magically showed up in the database here. So as a test I went into the UEM and made a new talkgroup, spelled it a certain way and kept that info to myself. No one knew I did it nor did i ever put it in a radio to show up on Unitrunker. A couple of weeks later it showed up here with the exact spelling.

I never figured out which of our guys posted it as it was submitted anonomously, but it did generate a nice email about COMSEC.

 

[Project25_MASTR]

Do you like AES? Because that's how you get it implemented.

 

[hiegtx]

So I know that they exist because obviously we use them, but coming from someone who doesnt know much about it, im curious, those who upload stuff to the database, how do y'all find that information? Is it just frequency searching and when a transmission comes through it gets written down along with the CC or VC or radio ID's. I've always wanted to know how it happens.

Information on talkgroups, especially on a new system, come from various sources.

Sometimes state/local/regional government web sites can have useful information.

While this particular source did not 'officially' come from the city itself, when Dallas (city) began the migration from their conventional Uhf frequencies, used by police & fire, among others, someone was able to locate a spreadsheet, showing the use and assignments for talkgroups that would be used by the City of Dallas, along with departmental assignments. That, of course, did not confirm how they'd be used. For example, Dallas Fire Rescue had two talkgroups, 32001 & 32002, designated for fire equipment dispatch communications. TGIDs 32003 & 32004 were identified as being for EMS Dispatch. Instead, however, DFR is using 32001 for fire equipment dispatch, and 32002 for EMS dispatch. (Dallas refers to EMS units as "Rescues", not 'medic, 'MICU', or ambulances.) That spreadsheet was only for Dallas (city) usage. Dallas County, as well as several of the smaller suburbs, also migrated.

To identify channel usage you need to be able to listen carefully, notice things and take notes.

What I do, with a "new" (not yet fully documented) system is set one of my scanners up to record all activity on the system, with the scanner set to "ID Search" to capture new talkgroups that have not yet been identified. Where possible (when at home), I also set the system to log activity via ProScan. Then, after letting the scanner monitor and record activity for a while (preferably several days), I import the recordings into my PC and analyze usage patterns with the Universal Scanner Audio Player. It presents audio files in a spreadsheet format, so I can sort them by talkgroup ID, creating a string of communications on that talkgroup, & listen for a pattern of how it is being used. Using the program, you can string together multiple transmissions on a specific talkgroup, and possibly finding a string of related audio files being used for a specific situation,

With logging, you can look at an unidentified TGID, which is in between already identified talkgroups. If 'talkgroups 101, 102, 105, 106' are used by a PD, then there's a good chance that unidentified TGID "103" or "104" is also being used by the same department.

Similarly, if you see a UID being used on your unidentified target, but logging shows that same radio ID being used on already identified talkgroups, such as fire or police, that's often a good clue that your unknown TGID is being used by the already identified agency or department.

 

[rattlerbb01]

Plus.....with Broadcastify calls, we are able to track individual RID/UID usage across talkgroups over a 3 month period which tells you who is using what talkgroups very easily. Now, a person running DSD+, Unitrunker, etc. to monitor the datastream can do the same thing if they are right there in range as well. It is very easy to play back the recordings and hear things like "Dispatch to Engine 41, go over to Ops 5" and then see the same unit number pop up a few seconds later on that talkgroup, and even easier when they say "Engine 41 is on Ops 5"

I would say that that is how we get about half the talkgroups in the database, but plenty of individual agency members will submit their talkgroups too. Just some examples here, but it may be a volunteer firefighter playing with his portable, or a teenager turning on his dad's police radio and watching unitrunker light up as he changes channels. We honestly don't get an appreciable amount of info from radio techs, at least in Texas and Louisiana that I admin for.....that is their bread and butter and COMSEC definitely is a much more serious topic to them, as it should be. However, the very basics are what we have for most counties out there so there is so much more to discover, but if you aren't hearing something, does it really exist??? It is good to have a list of a bunch of talkgroups to make the site look complete here, but if they are all encrypted full time, they don't really do the end user (scannists) any good.

 

[APX8000user133]

These replies have been very helpful to understanding this stuff better, thank you to all who replied.