How to determine all talkgroups affiliated with a specific P25 statewide tower site

[Cowley639]

Hey everyone,

Not sure if this is in the right spot, so move it to the correct section if not.

I'm somewhat new to this... I'm in an area where I can only receive one tower site of a large statewide 800mHz P25 (Phase 1) trunking system (I'm in a pretty low area,). I have a Yagi antenna pointed at the tower connected to a old BCD996XT. I would like to have a way to determine all talkgroups that are affiliated with the tower site I am monitoring (not necessarily at all times, but on certain occasions). Is there an easy way to do this?

I have a pretty good list of talkgroups now just based on the departments within the geographical range of the tower I am monitoring, and I hear a pretty good amount of traffic, but I'm sure there are more that I'm not aware of.

I was not sure if an SDR is the best way to accomplish this, or a scanner? I'm willing to purchase whatever is needed.

Thanks everyone!

 

[RaleighGuy]

Here is a similar question in another thread, check for your answer here

P25 towers and talk groups

I apologize if this has already been covered, I have looked, but haven’t seen the answer to my question. When I’m programming a trunking system, on a Pro-106 scanner, I have a scan list for each county I want to monitor, plus one or two scan lists for misc. state / federal agencies. I have a...

forums.radioreference.com

 

[Cowley639]

I guess I should add;

I'd like to be able to have a list of (hex or decimal codes) talkgroups affiliated to the tower at any given time, so I can cross reference them with the RR database then add them to my Scanner if I determine I want to hear the traffic on that talkgroup.

 

[RaleighGuy]

I guess I should add;

I'd like to be able to have a list of (hex or decimal codes) talkgroups affiliated to the tower at any given time, so I can cross reference them with the RR database then add them to my Scanner if I determine I want to hear the traffic on that talkgroup.

Then I should add you need to get a pen and paper and do a lot of logging and listening, and be aware it could change from time to time based on the system rules for affiliation.

 

[19-685]

PRO96COM will be very useful as it shows all radio IDs and their associated talkgroup affiliations on one of the tabs. It will also save to a log file.

Pro96Com - Control channel decoder for P25 Trunked Radio Systems

And it's compatible with your 996XT

 

[Cowley639]

Then I should add you need to get a pen and paper and do a lot of logging and listening, and be aware it could change from time to time based on the system rules for affiliation.

Yes, fully aware of that. But this doesn't help me with a solution...

I wasn't sure if there was a simple way to accomplish this with an SDR, and just get a list at any given time of the hex or decimal codes to actually determine the talkgroups affiliated with that tower?

 

[GTR8000]

If you're asking if the trunked site/system itself broadcasts a list of all active affiliations, the answer is no, it does not. The only way you could determine that to any reasonable degree is by logging the site 24/7 using software like Unitrunker or Pro96Com to see what subscribers are affiliated with what talkgroups.

 

[Cowley639]

If you're asking if the trunked site/system itself broadcasts a list of all active affiliations, the answer is no, it does not. The only way you could determine that to any reasonable degree is by logging the site 24/7 using software like Unitrunker or Pro96Com to see what subscribers are affiliated with what talkgroups.

Thank you, That was the info i was looking for... Reason for all of this is I know there are a few talkgroups in my area that are being used and are not in the RR DB, so I am trying to determine what those are.

There are also a few departments that have just recently started using the 800 system and are also not on the RR DB. I'd like to be able to hear them, but also add to the RR DB.

What's the easier system to use? Unitrunker or Pro96Com?

 

[GTR8000]

It depends on what hardware you have/want to purchase and exactly what you want to do with it. The latest versions of Unitrunker only work with supported SDR dongles, which are pretty affordable if you stick with the basic ones. Pro96Com is a bit dated at this point, and requires a scanner or receiver with a discriminator tap to decode the control channel. Unitrunker can decode P25 voice, but only Phase I FDMA, there is no Phase II TDMA voice decode capability.

Frankly, if you're simply trying to find and identify new talkgroups, you really don't need to track the activity at the site to look for affiliations. Sounds like what you really want to do is to record the audio of unknown talkgroups so that you can figure out the who/what/why. After all, what good is a list of raw TGIDs going to do you if you have no idea what the purpose of those talkgroups is?

 

[Cowley639]

It depends on what hardware you have/want to purchase and exactly what you want to do with it. The latest versions of Unitrunker only work with supported SDR dongles, which are pretty affordable if you stick with the basic ones. Pro96Com is a bit dated at this point, and requires a scanner or receiver with a discriminator tap to decode the control channel. Unitrunker can decode P25 voice, but only Phase I FDMA, there is no Phase II TDMA voice decode capability.

Frankly, if you're simply trying to find and identify new talkgroups, you really don't need to track the activity at the site to look for affiliations. Sounds like what you really want to do is to record the audio of unknown talkgroups so that you can figure out the who/what/why. After all, what good is a list of raw TGIDs going to do you if you have no idea what the purpose of those talkgroups is?

Agreed.

Thanks for the help. Sounds like my best bet might be to do unitrunker with an SDR.

 

[marksmith]

Unitrunker and a $20 dongle running and logging 24/7 is your answer but you will probably get some things that don't normally associate because of user radio association rules, their location and programming. Some TGIDs associate with all towers, regardless of where they are on a statewide system, and some only with a local site. You can't pick towers. Only sites.

Seems what you really need is a scanner, programmed with your known TGIDs programmed and locked out, and running in search mode. The only thing you will receive is what you are asking to hear. Everything else.

 

[BinaryMode]

What I do is program the voice frequencies ONLY as a "one frequency trunk" system from the two towers I monitor and set to ID search. I use ProScan so whenever someone talks on a voice channel I record the audio and the talkgroup as well as the unit ID (RID). Note that a voice frequency can become a control channel and vice versa. But doesn't happen all that often.

I've discovered numerous other talkgroups that weren't in the database this way. Of course many are affiliations from other areas. Those ARE in the database. What I do to try and mitigate the known talkgroups is program a group of 500 (the max) talkgroups that I see often and lock that group out. Now this programmed system scanning just the voice frequencies won't stop on those talkgroups (500 of them). There are more I'd like to lock out, but you're limited to 500 per group. Even if you had another group I believe it'll still lock onto a talkgroup that may not be in group 1 but in group 2. Edit- I'll have to check my theory on that because I may be wrong and can in fact add more than one group to lock out talkgroups. DMA scanners are different than what I'm used to...

Understand?

The power of ProScan allows you to use a notepad program like the awesome Notepad++ and use copy/paste to ProScan for frequencies and talkgroups. You can even massage data in Notepad++ in multiple ways including the use of regex (regular expression). You can go to ChatGPT and ask something like, "I need regex for Notepad++ that will delete duplicate lines." Though, Notepad++ has that feature already built-in under: Edit | Line Operations.

Hope that helps.

Edit-

If you go to the RR database you can go to File | Save in your browser and save the htm document for latter reference at anytime. I do this myself and keep copies for compare and contrast. I even have a script that will turn all the html <td> (table data) <tr> (table row) tags into a csv file for me. Now I can massage the csv data in Libre Office Calc (Like Excel) or Notepad++.